RE: OS 35FP-S Oil / Nitro Percentages
I have 3 FP .35's.
They all run fine on 80/20 or 75/25 FAI mixes (i.e. zero nitro) and produce acceptable power for the planes I've put them in. I've mixed various oil package zero nitro mixes ranging from all castor to 50/50 Castor/Klotz.
FWIW, OS recommended 20% castor oil for the LA .46 I bought recently. Manual claimed 5% nitro was fine, 10% if you wanted more power. I've found it produced plenty of power on a standard 80/20 all Castor FAI mix and have felt no need to feed it any nitro. It drags a 650 square inch stunter with a 2.5" thick wing section around with authority with no nitro while loafing along 4 cycling on the edge of a 2-cycle break.