I was very late to this hobby. Having been a PC, copier, printer and fax tech for 30 years, I just dove into custom keyboards last year. In the past months I have learned so much but there is still more that I will never even touch. There are some super slick looking 60, 65, 75 and 80% models out there but I really love big, heavy, full size boards in all their numpad glory. Finding custom models that aren’t made by Keychron is difficult (not that I don’t like Keychron, it’s a decent board but not custom enough). My first real keyboard purchase was a Monsgeek M5. It’s a great board, plenty of foam, solid frame, very easy to make it sound as loud or quiet as I want. What else is there? I don’t want or need another M5. I have a Keychron V6 and a K10 Pro. Who else does full size? What I’m after is an endgame board, something special that I can use everything I’ve learned in the past year to tune. All help/advice is greatly appreciated!! And if you have something you wish to part with, I would be interested in a transaction.
Carolina Mechanical had done a full-sized aluminum keyboard. It was all made here in the US which was cool, although it was rather expensive. Their shop shows as being shuttered at present so I’m not sure what the story is there. https://carolinamech.com/
Full-size isn’t nearly as popular among custom enthusiasts. Tenkeyless (TKL) and smaller tends to be the focus. So a full size custom can be something of a rarity.
I have seen pics of the Carolina Mech Fossil. Such a nice looking piece, sorry that I missed that buy. 
Do you need full full-size?
While complete 104-108 key is not super common in the fully custom space, finding a nice 1800 or similar is not as hard. Kbdfans runs the Odin at the high end, and they have its FRL sibling in stock now. There’s also the Brutal V2 from CannonKeys. It’s sold out in alumnium, but RNDKeys does the “Boston,” a compact battleship thet adds an extra row of function keys to a full 1800 layout. The 3D printed one is probably not “endgame” in the traditional sense. Then there are the occasional group buys like the Wind X98 or the Austin.
Below that, the Halo 96 from Nuphy is well regarded. Monsgeek M2 as well. The FC980 has various custom mods floating around the aftermarket as well. This thread is getting a little older, but there’s good ideas there.
I was so tempted by the Fossil.
Even the colours were great.
But I could not justify $600 just for the kit. Plus, it is probably too heavy for many of the surfaces I would put it on.
I hope they do another run, though. It’s true that full-size basically doesn’t exist in the custom scene.
If I wanted a nice full-size, what I would do is get the Keychron Q6 or the Monsgeek. But that doesn’t seem different enough from your existing keyboards. [Even though the Q6 is a different mounting-system than the V6 and is generally more luxurious. And both the Monsgeek and Keychron can be pretty heavily-customized in the range of quiet or thocky, and probably in terms of flex.]
So if I wanted something special, I would find one of those old Cherry full-size keyboards, and retrofit it. Apparently, HPs make them into a pretty ‘thocky’ keyboard. Or lubed linears like Oil Kings should be good in a plateless set-up. That would be a classic design, but with shiny new switches inside.
Or find a Wyse board that’s been stripped of its vint. blacks, and put HPs or something in there. Wyse is such a classic board, if you can find keycaps for it.
Failing that, a Cherry 11800 is not exactly a full-size, can be retrofitted in all sorts of fun ways. A ways back, there were even replacement PCBs for it:
https://www.reddit.com/r/MechanicalKeyboards/comments/e251pg/building_a_sleeper_g8011800/
Anyway, building a sleeper G80 is a huge option. The technology for making modern Ergo Clears alone is staggering.
Realistically, this is probably the best idea. I don’t frequently use all of those middle keys and could easily do without them all. I like the look of KBDfans Odin R4. Love the TKC1800 and its alternates but apparently there are none to be had anywhere, new or secondhand market.
Didn’t see anyone suggest this yet but you could check out the QK100 over on QK100 – qwertykeys
Thank you! I had an absolute brain fart and couldn’t remember “that one with a mountain on the bottom”. LOL.
You’re thinking too small. You need to go even bigger than full-size with the Hyper 7! 
Just look at the possibilities:
and look at the absolute CHONK from the side profile of the enclosed version:
On a serious note, not quite sure if that meets your specs, but thought I’d throw it out there just in case you had not seen it yet.
I have a pretty extensive guide written up for a 1800 and similar size board on this list there are some full size boards.
But if you really want a full size keyboard, you could consider this board. The designer and maker is local to my area.
If I had the available real estate, I would seriously consider it. However, not sure where I would find enough 2/2.25u keys to populate it.
That’s the fun part, I do think I remember seeing one or two kits at some point in time that were meant to fill out a Hyper7 but they’re probably not available anymore by now.
EDIT: Scratch that, this current run of the Hyper7 has an option to buy keycaps for it.
My ideal keyboard size is the 60-65% range (though I do have a FRLTKL and a couple sub-60% boards), so I don’t think I’d ever buy the Hyper 7. It’s wildly excessive, has about 100 keys more than I need, and would take up my entire desk, but there’s a part of me that desperately wants to buy it just for the weirdness and impracticality of it.
That said, echoing @Wooden-Toilet, further down that GB page for the Hyper 7, there’s the option of an add-on set of keycaps for $64.
You could also try to find DSA Ferrous or KAT Space Cadet Hyper7 sets on Mech Market or some other aftermarket. But I agree that keycap options for something like this are extremely limited. Please keep in mind that there are some differences between the “modern” and “classic” PCBs available for R4 compared to previous runs, so compare keycaps to the PCB very carefully if you go this route.
And yes, we are a bunch of enablers. 
Oh my goodness, I’m embarrassed I forgot about this one. Rucker’s work is great. I’ve got his numpad and it’s a very well done piece. I’ve long been meaning to get a full-sized from him.
KAT Space Cadet had kitting to fill out the Hyper7 as well.
Thanks for all the posts today folks, I really appreciate it. If anyone happens to see anything interesting on your favorite new market or aftermarket site that fits my needs, please post a link. I regularly check the ones I know (which isn’t very many) as well as the Marketplace here. Much 
to you all.
Going to shamelessly plug the open-source board I designed a few years ago, the Boston. The files are on Github here.
(thanks to RNDKBD for the image)
I wanted a board narrower than a full-size, with a full 2u zero and a traditional 2x3 navblock in a 7-row layout similar to the old Thinkpad keyboards. I added the extra keys and knob just to even the board out and make it a battleship.
RNDKBD still has the 3D-printed version, and previously sold the CNC aluminum version. You can also have it manufactured from the files on Github.
I did not know you’d open sourced this. That’s super cool.
I love the idea of the Boston, though I haven’t used one. In fact, I’ve been noodling with a no-stabilizers riff on it (I called it the Houston, LOL) that, at 18.5u wide, I could fabricate as a hand-wired sandwich on a cheap diode laser. You’d need fairly generous keycap kitting, but nothing exotic or even unsculpted if you can live with some oddities as the “spacebar” and the two Enter keys.
On a tangential note, how have you liked Alibre Atom? I am worried I would miss booleans too much to switch over to it, but the price for a mature parametric modeler is sure nice.
Ever considered Topre? There’s the norbaforce which might be up your ally!