[Patrick]

I've used 6s a bit in my truggy with a 1515 2.5d (1650kv) and a 1515 1y (2200kv). I like the 2.5d better for 6s. You can easily gear it for normal bashing speeds (maybe a bit under 40mph) and it has a lot of punch without having to worry about temps. Even when I used it on a 45C (113f) day it didn't get hot. When you want to show off just gear up a little if your batteries can handle it. As long as your not doing hard stop start driving temps should stay fairly low, for me motor temps didn't change when I geared up.
I don't know about in a revo, but in my truggy it's hard to gear the 1y for ~40mph on 6s, because the rpm is so high, so with my normal gearing (46/12) it is geared for ~50mph. But it gets to around 65c (150f) in 10 minutes, while my 2.5d would be under 50c (120f) geared for the same speed with the same type of driving and ambient temp.
1515 2.5d on 6s is my favorite setup that I've tried.