As you said, no limit: the only limit is my capability to afford his evergrowing salary and the will to sacrifice him for a long session of out-of-position training.But what was the point of buying him if not for making him a monster? :P And the only player better than a triple legendary big man, is a triple legendary big man who can also pass, shoot and defend outside :)
I bet you would go bankrupt before you could get him to triple legendary.If you stop at triple marvellous I might be in the market for making you a sensible offer!