I've been flying enough, I'm aware of all the hydraulic problems, tank issues. But haven't run too many RC engines upside down. One of the guys at our field has an OS 1.08 in a Spit that runs flawlessly upside down withough ignition. More concerned about the idle needle set up and wether it is effective or not. Not prepared to add on board ignition on a 25 size model. What Nitro do they use in combat or does it matter. I thought I might fly a few combat planes and then try and muster up some interest?? Our old control line planes we just started up side down. No thrortle though. Haven't flown many small engine planes for a while.