Need some help from the pros!

Here's the plan, so hear me out and help me try to solve my problem.

I am going to be building a SCX10, rock racer/trail rig. I plan on using a XL-5 ESC and Titan 12t motor out of my Slash as the power plant.

The issue is that I want to put an interior in the Hi-Lift body and need to shrink the size of the spur gear to do it. If I drop down to a 24/54 or a 21/54 according to BrianG's calculator I can hit the speeds that I am looking for. (7-cell NiMh and 2.2 tires)

I want to know if I will blow up the motor by doing this as according to the calc, it will be running around 30k RPM, and I always get the overheating warning when I plug any values into the 540 brushed motor sizes under 35t.

So how do I resolve this. I want the best of both worlds and have seen successful builds using the Slash power plant. But due to the fact that I want a smaller spur and a little more speed, I have hit a wall and need some pointers.

Thanks for all the help in advance and wish me luck as I leave for Iraq in like soon, like real soon.