RE: Fastest GWS plane......
I would glass these things, add dual carbon tubes down the fuselage and dual carbon tubes in the wings, overall I be you would add 3-4oz if you can glass these pretty well with a limited amount of epoxy!!! Personally I would buy the Formosa, its a better Design and a better flyer in my mind, The P-51 looks great and flys fast, and thats about it......The formosa is that and also is a very good aerobat, It's a better plane overall, unless you have a thing fro warbirds!! Good Luck,
PS here was my Formosa(sold)---now im into the 3d planes(Tensor 4D) and My FT 90........
Himax 2025-5300, Cobri Gearbox(6.6 to 1), 3s 2100 mah TP lipo, CC-25, dual aileron servos-----Fast , vertical launch, nice precision aerobat!!!!
They have really good Videos of this plane and combo over at e-flightline,
[link=http://www.e-flightline.com/movies/Formosa%20Dave.wmv]Formosa Video![/link]