The Twin Mustang is definately NOT aerobatic. Even with ONE engine, the wing area is overloaded. With two, it's purely a speed plane. This is the Scientific model, not the Brodak.
Currell Pattie's plane won a hollow log speed contest at 66 MPH with two Fox .049's. The best single around here did 63 with one Black Widow.
If you get two healthly 1/2A's going at the same time, you have a .10. Build it with that in mind.