I follow alanbass's approach when putting on Schallers: trim away excess leather to insure a snug fit.
Also, and I have been playing with Schallers on all my instruments for 20 years -- you just gotta check the nut to make sure it has not worn loose. Just like you chck your amp knobs, instruments knobs, tuning etc -- add this to the warm-up regime: check to make sure the nut has not loosened. Really, though, even without the strap locks, I always check the old knob anyways for I have found that can loosen over time.
So no problems here -- just keep everythign tight and snug and don't worry too much about it.
I'd put Schallers on all my future instruments unless I saw something that was 100% better. Tried and true.