Before you start changing tanks, try a 21x12 or a 22x12 prop on it. You will notice you dont need all the RPM to keep the same speed, and it should run a little cooler. They like higher pitch props. I dont know how much time you have on yours, but it makes sense to leave it as it is for now until it has 'loosened' up a bit. Just make sure you check the valve clearances regularly until it is bedded in nicely. You also need to check the lubrication on the No1 valve train, especially the exhaust valve. It gets very dry in its std configuration.
I still suggest to everyone they should conver the engine to the negative crankcase modification, but each to his own.