I think having the muffler pressure on the bottom wouldnt make that much of a difference. If it does, you could probably try and tap the top of it. You might as well get another muffler considering a new quality one would make much more power. Good brands to look at would be ksj, hattori, and curtis muscle pipe 2. Helimax also used to make a good cheap muffler that sold through tower hobbies if you dont want to spend much money on a muffler. Heliproz also has some good low priced mufflers.