I don't know how much you weigh or what kind of hills you have. I weigh 165 and some moderate hills. The engine does not scream at 22 mph and no problem with the hills. However there are times that I would like a even lower tooth sprocket. However I would lose some hill climbing ability. the sprocket with the adapter was $48 plus shipping.(actually very reasonable for the Hi quality of the product). You can purchase the sprocket only, but it is not setup for the 9 bolt rag mount. They would probably set it up for you but I have no Idea of the turn around time.
To make a long story short, I would favor a 32 over a 36 anyday. I have put a five speed setup on my second s-OCC. I have ordered another engine for it. My only worry is putting that much load on a standard bicycle chain.