I moved as much as I could behind the cockpit.
I added a 4 cell 3500ma battery for a flight pack.
Mine balanced perfect according to the book.

I'm re-doing the the muffler.
Extending the stinger, slanting it back at a 45 degree angle and increasing the diameter 1/8th of an inch.

Perhaps this will help keep the plane a little cleaner and build some low end tork.
The stinger didn't extend far enough past the firewall.
I ended up with a lot of black goop on the bottom wing.

This the before picture.