Kris,
I use the stock banjo muffler from BME. It is louder than a pitts but is light. Do you need it to be real quite? I weighted my 44 with everything needed to run including nylon/glass mounts shaved down to the max but without prop or spinner and it way 3lbs and 14 oz. Very close to 4 pounds and that was on a postal scale. The battery is a 1000 mah sanyo nicad. How many square inches is your models wing area? My igntion battery is back on the CG btw.

Joe !~)