I already posted this on another thread but...
If you are not limited to the 15 engine try the House of Balsa P-51 Mustang (the larger one) with an OS 32SX shoehorned into it and wings clipped by 1 rib per side... A cheap, agile and very fast plane that doesn't look too bad either. Verticals are totally out of site. Thrust to weight is about 1.3 or so if the engine is running right. (an APC 9x7 prop will turn at 14.5K in the air)
We clocked mine at 111mph.
Stick all the hardware as far back as possible and make sure to use spruce wing spars with a healthy amount of glass at the joint.
My next one is getting an OS46 FX. Planning to mount it right in front of the wing with a shaft extension to preserve the sort scale look and not go overly nose heavy.
Here's a pic, Kelly W
(PS: Speed was measured with Doppler effect)