Actually the clothes bones aren't connected to anything.
I had one more go with playing with lattices and bonevelopes for the croptop rig, and then went back to the straight bonevelope rig and added a few more bones and made all the bones smaller and with smaller envelopes, as I had a lot more control over the shape and the twists of those annoying little shoulder straps with the bonevelope rig. It's holding shape a bit better.