RE: Changes?
Dart,
it is not uncommon for there to be variations in manufacturing where one engine has a touch different tolerance than the next. You can try mixing equal parts of your 30% with your 10% and that will yield you 20% fuel.
If you are getting detonation, it is indicating that you have too much compression in that engine, or too hot of a plug, or too much prop load, or too much nitro, or too lean of a needle setting. OR a small combination of more than one of the above. Teh easiest solution is to richen up the needles, if that does not cure it, lower the nitro content or go to a different brand or heat range plug (cooler).
Hope this helps