When that engine first came out, RC Report magazine did a review on it. One funny thing they found was that if you added a length of silicone tubing to the end of the muffler (I forget how long but I think it was 12") there would be quite a power increase. Aerotrend used to sell the tubing. I don't know what would happen if you pulled the rear baffle out. I think I've only had one of those apart and there are several pieces to it. It might not even be possible without gutting the rest of it. Darn effective muffler and feather light too. Be careful of the nut at the front holding it all together. It's pretty easy to break the piece of all thread when trying to unscrew that nut.
carl