Hi Mike

I think it is not a good idea to wrap the HD motors in anything at all as they are getting very hot.
Secondly, if you crash, all the force is distributed to the one motor you hit on and will more likely break the motor mount, or even the center cross, and will also not prevent the rotors from hitting the ground.
Have a look at my solution at http://www.rcuniverse.com/forum/m_5097494/tm.htm