I had both the smaller (52")and larger (80") OV-10s, both had glow engines. I added 4" to the wingspan on the smaller one, it was powered with 2 OS .25FX motors, plus it had Spring Air retracts. As I recall, the RTF weight was 6 1/4 lb, and the plane flew great! The 80" Bronco had 2 OS .91 Surpass motors and Sierra Precision retracts.
I never had an engine out, probably because I was careful to make sure each motor was slightly rich on top end and had a good idle to full throttle transition. Careful tuning is important. Note, I could also practice a quasi engine out scenario by throttling back either motor to idle during flight. The OV-10s are manageable on one engine. The larger OV-10 also handled like a twin engine trainer, very smooth. When you install the main gear, move them slightly forward of what the plans show, it was difficult to rotate for take off in the original position. That's my experience, I hope it helps!