ORIGINAL: XJet
You are correct that the needles will be a little more sensitive with low-oil ratios but this should not be excessively so.
We run 5% nitro in our 2-strokes and 10% in our 4-strokes. With this small amount of nitro, perhaps our needles are a little less sensitive than when on a 0% nitro blend.
Hey XJet.
Have you tried skipping the nitro, and using a total of 18 % oil instead? Then your fuel costs perhaps will be lower and your engines easier to adjust.