Graham,

Your 10% run sounds very much like how my PAW 19 used to run on 10% ether fuel for sports c/l flying. For cold starting it needed a fraction of a turn in, but once warm would re-start on the running compression without any adjustment.

Compression setting on the low ether fuel was more sensitive than with the normal 1:1:1 mix, which seemed to have quite a wide range of viable compressions for usable power.

I never went below about 25% oil (may have experimented with 20%).

Regarding Redex, my understanding is that is an upper cylinder lubricant and detergent, ie. it both assists with piston/liner lubrication and with de-carbonisation.

Is it really necessary? I don't think so, but it doesn't hurt, and definitely seems to keep carbon build-up in check. It is also fantastic for freeing up gummy engines - a little bit down the venturi and the engine becomes much freer to flip over.

cheers,
Colin