Looking at you latest set up I see now you went from two bolts to three bolts for mounting. The back of the front holes could be slotted so you wouldn't have to remove those bolts ( just loosen & slide off), but still keep a solid mount there. Also instead of through bolting the box you can drill and tap or weld a nut on the bottom so you don't see the bolt. It looks good by the way and should serve your purpose just fine.
