OK, so I've got this 30% Paulistinha P-56 ARF and I plan to mount my Seidel/UMS 770 radial. However, when I align the UMS mounting diagram with the lines on the model's firewall (intended for a 50cc gas engine), the top bolt on the UMS mount would be above the top of the firewall.

So there would seem to be two options: 1) somehow extending the firewall upwards or 2) lowering the mounting bracket by about 1 inch. There's room to do this, but I'm wondering what the effect would be on lowering the engine's centerline. Does this affect the aerodynamics?