The setup looks fine except for the battery. I'm not a fan of NiMh either. That being said your ignition pack is on the overkill side. If I were setting up a 20cc airplane I would run a single 3000 mah LiFe battery. Your RCEXL opti switch can be modified to switch voltage via TX and I would also do that. Separation of components is pretty much a thing of the past but as always be sure to do a thorough range check.