Most of the MX spacebars of 6u sizes come with an off centered stem for older Cherry G80-xxxx boards. Topre boards have centered 6u spacebars so I add center stems with epoxy.
Most GMK kits with extra spacebars include 2 x 6u spacebars now, one with a center pole and one off center.
Here’s my mod link : Fixing warped PBT space bars - #14 by AdrianMan