Depending on your temps now, I would try 18/68 first. Have you seen the outrunner-inrunner hybrid thing on hobbycity.com? Seem like those might be pretty friggin strong if they have the torque and power of an outrunner.
Yes, I've seen those. I believe it would be pretty easy to overheat those. The internals don't have enough contact with the can. Lack of airflow leads me to believe it to be a fragile motor.
I have had great success in the AXI line of 12 pole outrunners. Even with the smaller 2826/8 motors in the E maxx.