Great job. I have seen a lot of hacked up cowls (even ruined a few myself) but yours is excellent.

I've never bent the muffler tubes on purpose but I don't see why it wouldn't be possible. My main concern would be collapsing the tube or breaking at the point where it attaches to the muffler. Of course, a few flat spots or kinks in the tubes probably wouldn't hurt much besides looks. Maybe you could take the muffler off and pack the tubes with sand to make them bend smoother without kinking? Perhaps one of those spring type tube benders might work? Who knows, they may bend smooth just as they are.

Where abouts in the Philly area are you? My wife is from the Norristown area. We are going to visit her family in June and I'm going to try and sneak away to some flying fields in the area.