Well I've just run mine again on a Cox 6x3 yellow nylon. Still runs hot, and quite a lot of vibration. Its not a Mills 75 by any means in terms of starting-but at the same time-completely normal diesel responses-it's quite critical for optimum compression setting-and lets you know very quickly when even slightly over-compressed-by labouring quite markedly. Needle is not of the 'precision adjustment' variety (nor was the original Frog 50!)
Best revs at this stage on the 6x3 (which is the recommended running in prop) were 6700rpm on Model Technics D1000 homebrew. It could not run out a tank before overheating and stopping-so there is still plenty of running in to do-and Ian's recommended fuel mix (very high in castor) is clearly needed for this phase. [see scan of instructions attached]-I'll mix some of that up, and hopefully do a few more runs tomorrow.

ChrisM
'ffkiwi'

PS Even at 6700rpm there was plenty of thrust coming off the 6x3 Cox-certainly enough to fly a suitable small light model.