I didn't change the thrust angles on my Contender. It seems that there was some downthrust and some right thrust built into the firewall already (gold edition kit). Rotating the engine won't change the angle... I'd say go for it if you want!

I strengthened several aspects of the plane, including the structure of the tail-feathers. But then again... I intended to put a larger than specified engine in it. Careful though... its easy to add weight.