Yo, Viper....
....the Ys .61 should be pretty good, and faster than
my plane. I run an O.S. .61RF long pipe in a Kaos, and
the "long-strokers" run sweet. For a two stroke engine in
the Mustang....That sounds like a really good choice. I
noticed in an ad the other day, the WM mustangs are now
rated as .46 to .61 engines (2-strokes). With the fat spinner
a 12" prop is about the minimum.