82dB(A) is the National UK limit for noise from an R/C aircraft. Measurements are taken at all 4 sides of the model, at a distance of 7m (22' roughly) from the model. so at 10' that's about 88dB roughly that has to be met.

People in my club with an Irvine 53 have had success using the standard silencer in its full form (not sure if you modified the silencer or the model to make it fit) and a 12x7 or 11x8 APC prop, but you can also get through with a 12x7 Graupner. FWIW our club imposes an 80dB/7m noise limit on all models <1cu.in, and in general the main solution is to run at less than 10k rpm, which obviously makes 4-stroke engines our preference!

Regards

Chris