From the holdfast blog:





Holdfast on a mks track pedal. Very similar to other track pedals. GR9s may be tricky though. Especially without the hole in the front to feed the strap through. I put a longer bolt through my toe clips on my GR9s and it acts like a "hole" for my double straps. However I have no experience with holdfast so I'm not sure if that would work. Holdfast straps also seem bulky to fit onto a GR9. I may stop by my LBS and see if it's possible since they carry both.