Well, up thrust isn't going to help anything. It is a flat bottomed airfoil and I know that our spad planes with a flat airfoil on a flat rail with neutral elevator at stall would also pitch up. Man have I seen enough of those loop back over. It's possible that if you had caught it with down elevator till it picked up speed that it would have been a different story. Also, I imagine you launched full throttle? Nothing wrong there but it does make things happen pretty fast. In combat I'd launch full throttle but I'd also give it one heck of a javelin throw. That did several things for me. First, it got my ship over the pitch up speed. Second, I looked AWESOME with my hand catapult style. Third, it really helped me physically get rid of too much adrenaline. Oh, my knees would be knocking in a couple minutes just from the excitement but with the throw, some of that anxiety went away.
Things too look for. First off, elevator straight. You've looked at that. Second, Ailerons drooped any? How about dialing them up just a little? Trust me on this. If those rons are dropping just a bit you've got a pitch happy bird on your hands. Folks that fly with flaperons are used to this. Drop the rons and you can make some steep, slow approaches but get close to the ground, decide to go around and nail the throttle, you'll swear the thing was the seat of a swing it pitches up so quickly. Then chop the throttle and guess what, you stall, your nose drops and you've just planted your firewall. On the other hand if you get a couple degrees of up on the ailerons and you've got Spoilerons. Your air speeds increase and your pitch sensitivity decreases. That helps smooth out the flight characteristics of a flat bottom wing a bit.
But my guess, wish I could have seen it, is that you let go without enough throw, with the nose up a bit, the low wind gets under the wing along with the upthrust and it simply pitched up and over and you didn't have enough speed or forethought to fly it out inverted. If I had a nickle every time I did that with a SPAD Dogfighter, I'd have eight nickles.
Rebuild it with the firewall neutral. Check those rons and sub trim it even. Don't launch full throttle, half will get it away from you and fly it fine on this design. Try try again. This is a wonderful flying plane from a bunch of different reviews. You've just gotten bit somehow but circumstance.
