PilotFighter,
I have a Webra Speed 60 with an older "flow through style muffler, and it too didn't supply pressure to supply a Dynamix carb. I solved the problem by first plugging the open front end with an old 35mm film canister top, and then sawed notches and "pinched" in the reart cone to restrict the exhaust opening. Together they increased the muffler pressure enough to run a Webra Dynamix carb on the engine with no pump. Hope these ideas help.

If your club doesn't have specific rules governing noise levels I suggest you do what our club members all do, and it involves something as simple as common sense. If it sounds too loud it probably is. Your fields neighbors are the ones you really want to shield from noise, because they are the ones who will take action to shut your club down if the noise gets to be a problem. Sometimes an engine isn't the most noise either. I run a Webra Speed 60 with a muffled tuned pipe on my Dirty Birdy, and trust me the "prop" makes the most noise! Good luck with your finding a solution, and PM me if you need more on how I modified my muffler.