I am flying a SS with a OS .91fx 2 stroke. What are others using for props and what engine head temperature should I look for?

I have a 15-6 on right now and I am overheating I think. I have the cowl nostril cut all the way open and the air flow area and path look great. I am going to experiment with props again...already did but more for performance. I think I might be over or under proped for how I fly. I know I fly with full throttle a lot latley. I am wondering if I might also just be running the engine too hard. I could also just be too lean. I think I am pretty rich by my tuning opinion but that is what a temp gauge is for.

So more than prop size a target temp would be what I need to know. I have read other threads about what range of props guys are using.