Quote Originally Posted by EddyCurrent View Post
If the top rails hadn't warped through welding the 10mm thick steel plates for the bolts, I think I would have been able to shim it without the epoxy.
Yes I agree and it was the thick plate and current required to weld it that caused warping.
I don't weld plates to the top rail I just insert thick plate on inside and tack to hold then bolt thru it. That's also why I use Epoxy putty to give a nice matting between top rail and mounting plate on frame along with setting rails on same plane.
Often I don't need to use epoxy but I do anyway has it forms a kind of register, the only thing you need to take care with is that the top rail doesn't lean but that's easy sorted with holding plates until it's set.