Perky uses .15 engines and is thus an "A" event. Dimension A is therefore 1".
Fox 35 Stunt is a class C event so dimension A is 1-1/4".
Dimension A is the length of lines wrapped by copper wire at the the termination.
These rules were made for all-out high performance planes that can go 200 MPH. Perky & Fox only go half of that, so you're plenty safe enough.