My bolts were mangled as wll, so I bought a couple of 1/4" x 2.5" carriage bolts and lock nuts to replace these. Also bought a foot of I think it was 3/8" fuel line and cut two 1/2" pieces to make the bumpers. Bumper should add these bumpers to the kit :-)

On Tuesday, July 25, 2017 at 6:24:43 AM UTC-7, OHM Ω
- My original aft rail to frame holddown bolts will need to be replaced due
to getting terrifically mangled from, I think, repeated ramp deployment
collisions. I heard that there are also suppose to be rubber bumpers on
these bolts inside the rail but mine are missing in action. Might have
been destroyed due to all those collisions!
Picture at http://aviation.derosaweb.net/bumper/SRS.

Bottom line: Well worth the price!