Ya won't need it. I had mine setup with a Mega 16/7/7 motor and it was about as fast and as powerful as it gets. Heavy too at over 20oz.
Check out this video of mine without a spar (right-click and save-as...)
and if you still think your's will need one afterwards, then I'd suggest putting it in where the servo cables go and either put your cables on top of the spar or simply tape them flat to the wing and paint over the tape.