Mitty,
Put the flywheel on a lathe and turn down the fins to the same level as the hub of the flywheel. If you are accurate, balancing should not be a huge problem. I have never considered disturbances caused by the flywheel being a problem - the reason you turn them down is due to weight saving measures.
i didnt quite understand how to do this and i rushed it. i completely shaved off the fins on the flywheel. all thats left is the magnet and anoter chunk of metal on the other side. i think i screwed up. will the engine run with no fins? i cant start it right now becase i dont have a conversion kit yet so i cant attach a prop.