I am using an 11 X 5 (good low end torque) and a 10 X 7 (for speeed) with my LA 40. Maybe a 3 blade would be better for your "air truck", or at least let you lower the CG? Also, it seems to like at least 15%, and the air bleed is right in the middle. Also the # 8 plug is hotter, and likes that better than the A3. Your burned oil problem happened to me too, from being run too lean, it's hard to get off, but also have heard the crock pot & antifreeze thing will clean it. I haven't tried it.