Compression readings using a compression guage are useless other than as a comparison on the same engine using the same guage over a period of time for an indication that it's wearing out. Compression guages have a dead volume which effectively adds to the volume of the combustion chamber so gives a false indication of actual compression ratio. In a car engine this dead volume is of no consequence compared to the size of their combustion chambers but a 60 engine will have a total volume (including squish volume) of close to 1cc.

AFAIK there are no charts showing how much nitro can be used at a given compression. The only guide I could give is that I know (from experimenting) that 13.5:1 is ideal for zero nitro and that most engines using nitro have a compression of around 9:1 where they seem to be optimum with about 15% nitro. Some 4 strokes are (I believe) down around 6.5:1 and they run best on 30% nitro. Going by these figures I'd suggest that for 10% nitro a measured (calculated) compression of around 10-11:1 would be close to ideal. These calculated compressions are done by using the swept volume of the engine, not from where the exhaust port closes.