RE: Too much oil.
We use 5% nitro in our 2-strokes and 10% in our 4-strokes because it makes them nice and easy to tune.
With the lower oil content, it gives us the equivalent of 10% and 15% respectively.
With the nitro-shortage really starting to bite (I managed to score 4ltrs today the very last that I could find) we may go back to 0% for the 2-strokes but the 4-strokes really like that bit extra.
In winter (I'm in the southern hemisphere) our engines seem to run just a little too cold with 0% nitro, regardless of the oil content.
I know that because right now we're out of Cooper's oil (with little prospect of getting any more) so we've gone back to using Morgans castor/synth blend at 18% (nitro at 5%) and the loss performance is *really* noticeable. People are moaning at me that their engines just aren't performing like they did before. Going to 0% nitro with 18% oil will really knock the power-back on most of the engines we're running (TT46Pro, ST90, ASP 52, etc).