Christ, I had similar issues with my electric chipmunk, and tried a few things to get a better idea of whats going on.
Have you tried it with the top hatch off? This will give you an idea of whether you need more exhaust area, a radical change in temp will show that, considering yours is built like mine (or should I say I copied yours almost verbatim) I think you'll find very little change.
Adding a cooling disc to the back of the motor can help create a centrifugal pump out of the the back of the motor.
Emax have them as part of the stuff you get with their GT motors, but I suspect a fine modeller like you could make one out of carbon in a few minutes.
Be careful that you don't stall the airflow out of your motor, but have a 'cooling spinner' at one end and a disc at the other, I'm pretty sure that cooling spinners acutally pull air forwards through the motor rather than let it flow through.