from the pictures, it looks like you are utilizing the stock foot control/ lower motor mount bolt (which without the stock foot controls mounted would have plenty of extra room for a bracket) , and the upper bolt on your rear set bracket is what appears to be the swing arm pivot bolt which doesn't have anything mounted on it normally. so I am wondering where you are getting the extra length from on the upper mounting bolt for your rear set mounts.
just curious as my swing arm pivot bolt and all the other CB750's that I have encountered don't have enough length on them to make a bracket like this