I think the plug was leaking around the seal and that's why the last couple of outings were such a headache. Reassembled the engine this evening, put the plug back in and flip flip.. hmm, that doesn't feel great.. losing compression at TDC. Where is it going? A few drops of WD40 around the plug base and ta-da! Tiny bubbles..
Swapped plugs.. leak gone. Tomorrow I'll fire it up with the new trimmed and balanced 4x4.5 and see how it behaves. These Profis are pretty trouble-free.. prolly a simple dum dum like that. Hope so, like to fly it some more this season. Haven't accomplished more than fiddling with it so far this year.