I propped it "back" to an APC 12 X 8 and increased the throws to =/- 15 mm on the elevator (I had it set at about 10 or 11 to be conservative) and the airplane flew two full tanks tonight like a completely different bird. Increased the aileron throws a bit as well, and it just got dialed in, like on rails. Probably a case of just a few things off a tiny bit, and some nervousness on my part which resulted in a twitchy first few flights.

Ensure your throws and CG are set to specs and all should be fine...