Actually, size maybe relevant. Maybe just too big = fail.
Let's say Pcad's issue is soft tissue...overuse. Load path maybe bad.
Too much weight + poor saddle fit... seat height a bit high, setback maybe contributors.
Cycling by its nature of repetition leads to injury if everything isn't right.
PS: Shimano is speculated to be working on a pain damping device that interfaces with its Di2...targeted for older riders like Pcad who can afford electronic shifting. Small needle like probes are placed into pain centers of the body and a rider can shift up or down depending on pain level during a ride.