Got all the little mods finished up on the box blade today and tried it all out. Works great! First thing I learned: it's going to be necessary to unhook the box blade on some 4x4s or a pallet. Else it's too low to the ground to get under with the QH hooks. This time, I had to lift up the front of the whole tractor with the FEL bucket and skid back under it!
I have about a 1/4" to 1/2" gap between the bottom of the top pin and the top hook when the lift pins are securely bottomed in the lift hooks. That's about right, right?