I went ahead and drilled two 1/2" holes into the canopy and used some 1/2" flat washers on the fuselage. I epoxied both the batteries and washers in place. This has made for a very tight fit and looks like it is going to work just fine. O by the way the plane is a 1/5 scale Fokker D-VII with a DEL-30 gas engine. That is why I choose to use 1/2" flat magnets. Here are a few pic's The canopy has the pilot in it.