Old Fart, tried the 30 in the Rainbow but liked the OS 20 (4S) better when it was fitted, almost similar performance and given we (my mate and I) don't race around the circuit when sport flying it was the best combo for us. On the glo plug thing WHY don't people (for "normal use") use the factory plugs or at least the factory recommended plugs. I use Saito plugs generally and OS F plugs for performance. Never had a problem with all the various fuel mixes that I have used. I once used an Enya 3 with 50% + nitro and that was interesting once I got it to run. Sold the engine soon after to a person desperate to have it. Wood ducks are every where.