I have seen people online go to 16" on Moomba but get prop burn, others have gotten lucky and not had it happen. Skiers Choice does not recommend them with Moomba as they have different clearances. a 15.5x14 should be more than enough for any ballast you are running.
15.5x14 is not enough prop if you are running at the target pitch of 9.5*-11*

I tried a 3407, (15.5x13) it would pull the weight but when pitch was 9* or more I was at 4400 RPM.

I currently have a 3829 on the boat (15.5x14.5) and on the regular side when pitch is at 9* it drops speed and will not hold anything above 11mph.

Sure I can bring the bow down to hold speed but 6-7* of pitch is not ideal for the most push.

I have been chatting with mainly Moomba Max owners and not a single one has gotten prop burn with a 16" prop, I did hear of 1 Makai that got prop burn but also another Makai did not get prop burn.