Higher kv vs. taller gearing

[What's_nitro?]

I think you could go with the 9XL and keep the 4s batt. for now. I've noticed it's a fairly common setup in this forum. I'm not familiar with the Yusa buggies. Are they as heavy/heavier that a Revo? That's what I see the 9XL/4s combo in most often. You should be able to gear it for the same speed as with the 7XL and notice a large drop in motor temps. I'd advise against any lower kV to avoid having heat issues with the MM and being back to square one, unless you want to up the voltage a little...