I've heard of heli pilots improving range by shielding their RXes with tinfoil (presumably by keeping the RF out). So it's possible that trapping the RF by wrapping the motors might help...but in some ways their already wrapped in cans, so the leakage would only be at the brush housing and through any cooling slots.

Course, if you insulated the RX with electrical tape or something, you could try wrapping it with foil as well.

D.