I have BK fixed mounts and sub strap bars. I think they’re great..other options look like a PITA to use, but I can install or remove my seat in less than five mins. You can also get pretty low with them.
You probably have a different body shape than me, but I think Racetech seats fit me very well and are the most comfortable seats I’ve sat in.
Edit: I’m looking at the dimensions of the standard sized seat, and I don’t see why it wouldn’t work with a BK seat mount. 400 mm seat width would work with the 395–409 mm mounts. If seat width is staggered, you can add washers to square up the seat mounts (someone let me know if this is an acceptable solution)? I think not using RT seat mounts will make the setup non-FIA compliant, but I don’t think anyone here is competing in an FIA racing series.
https://racetech-usa.com/shop/seats/...torsport-seats