Still it will only give the SG of the blend. Not the nitro percentage. More elaborate tools are required for that....
Unfortunately there is no quick and simple way to check nitro percentage in a blend of substances. This will always lead to the possbility of adding nitro until you reach the max SG specified by ROAR/IFMAR end EFRA. Although they do specify a maximum nitro percentage by volume which makes all those that add nitro and go beyond the 16% by volume, cheaters.
But when the measurement doesn't say you cheat you don't....?
Only controlled fuels take this problem out of the equasion. It can add a lot of others though