Your right, it does say 10. I saw somewhere around here that it was 12 :032:.

What do you reccomend for a slipper?

Any cell count above 5 (6v) will create heat on a built-in BEC since they are linear. More cells, more heat. I'd rather use the heatsink on the ESC for the important part, the motor controller, rather than heat it up for the BEC function. I'm only running 6 cells (and 2s2p Lithium) on my Mamba max and I am thinking about getting a BEC since the heatsink on the ESC is so small. Just a little extra insurance. Plus, a digital BEC is more efficient and will help increase runtime (albeit negligible I'm sure).

Go with a Strobe slipper if you can find one.

Any other slippers that will hold up to brushless?

Not really. The Kipster is good but out of production as well and even harder to find. The RRP locked down with a modified Mod1 spur is the next best thing. I would assume you can modify a Ofna spur for the Kipster as well since it uses the RRP spurs.

Not trying to be picky, but I think that you might have the pinion gear switched around (12/66 - 5.5 ratio, 16/51 - 3.19 ratio)(16/66 - 4.13 ratio, 12/51 - 4.25 ratio).