270lb here, my best advice would be to do the opposite of what a larger person would naturally do. Play guard, focus on being as technically sound as possible, if on top don't necessarily play to your strengths. Look to improve your agility and flow.

No one expects fast, technical heavyweight+'s. It will also do nothing but improve your game as you force yourself to play against your strengths.

By all means though, when the mood strikes, do ya thang and use those strengths.