RE: G20 stock ignition versus RC exl system
To back up what Bill is saying I routinely run my gas/spark converted Supertigre 51 over 15,000 every time I fly it. Never had a single ignition issue other than a fouled plug which happened at 35 hrs. Second plug at another 38 hrs and it's still on the third plug. That's a lot of hours at 15,000 and no probs.
P.S. I race club 40 pylon and this is a good practice plane which is why I run it at WOT so much.