It looks good to me, I would go with that setup like it is. I would only try the 3w can muffler if the people at your flying field say it is still too noisy for them. If they aren't complaining, you are good to go.

Nice setup on the engine. We used to convert the trimmer, engines etc. to glow engines many years ago for giant size planes. At that time we had no electronic ignition systems and you either used the heavy flywheel magneto ignition or ripped it all off and went with glow fuel instead. Many of us used Perry carbs and made Perry carb adapters for the engines. But one could use whatever was handy for a carb at the time too.

I would make a mark on the drive washer to engine so that should you ever need to take it apart you can align it back up easily. Plus it will let you check it after a while to ensure it didn't slip on you too.