I'll have to agree here. Going nitro to electric is easy, the other way around, dangerous. Electric helis use thinner components because they don't have to deal with the weight and stress (vibration) a nitro engine puts on the helicopter. It's done like this to conserve weight (just about every electric heli is lighter than it's nitro counterpart).

Like vince said, if you wanna fly nitro, get nitro. Converting is just asking for trouble.