Sounds like a decent plan....despite spinning the same RPMs I would bet you'll notice a TON more power from more efficiency and higher voltage. You'll also get longer runtimes from a more efficient motor pulling fewer amps. I already own a Medusa 50mm and it has holes in the can, which will allow dirt inside the motor. I already got a RC-M heatsink clamp for it and I'm going to cut up a big washer to clamp to the back and hope that keeps enough dirt out of it
And now, onto the real problems: Traxxas doesn't really introduce new RCs, they just replace a few parts and sell it as a new RC. The Slash will probably go through parts rather quickly with that much power, their design is virtually bullet-proof for brushed motors but when it comes to BL motors you will strip diff gears, break output yokes, twist drive shafts, twist the yoke off the stub axles, and strip the hexes out (go with aluminum and you'll start stripping wheels). I know this for a fact because I have a Rustler with the same exact transmission as the Slash and with a MM 5700 I did all of the above
