Quote: Old Feller "Is that due to him not working hard enough in the gym, poor work by the conditioning staff or the lack of off season time?'"
Ideal playing weight is very much a personal thing. It's also not necessarily indicative of strength - few people would say that Hardaker struggles in collision despite "only" weighing 87kgs.
He's not particularly tall and he doesn't have a big frame, so maybe he and the conditioning staff have found a weight at which he feels comfortable and can be effective.