Looking at my own fingers, what strikes me is that the calluses don't extend all the way around, they are only on the very tips.

So I would say that you guys are on the right track by working on the curvature of your fingers to solve the problem of not having enough space for your fingers.

I have been playing guitar for 30+ years, but when I try to play the piano I wind up with the same problem you are describing. :)

Have fun.

Jon