The reason you are going through plugs is because the rod is stretched. When this happens it tends to over throw the piston causing the plug wire to be smashed because of the explosion of the Nitro methane. Nitro has an extremely fast burn rate, and the engine must be in very close timing to keep this problem from happening. Basically the explosion is happening before the piston can reach down stroke and it must go somewhere. You need to remember it is going 30-40,000 RPM's it doesn't take much.
Also could be running very lean and the intense heat ruins the coil.
Take off the back plate and see if the rod has an egg shaped journal where the crank pin is.
my 2 cents
Also LHS mean*** Local Hobby Shop.***