The spur change will give even another 1 mph, it will sure run things a lot hotter. If you are on a nice large, smooth lot here you used to top out real easy and quick then it can probably handle it. Getting some cooling air past the motor will help if possible and if the motor always ran real cool to begin with you'll likely be ok (and faster)

The problems with wires, batts, motors, esc's start to crop up the fastr you go, but I thik you are still well within reason.