My newest MM that I got last week works VERY well. It's been sitting at the LHS for probably a month or two, though. It seems like this one is a lot smoother with the Neu 1512 2.5D (2000kv) in my Hyper 8 on startup. 4s is no problem on with (with an external BEC, of course).

I was looking at the specs again I think my 5s A123 pack will be okay...it sits fully charged around 16.6, and the mamba is rated for 12 nimh which at top charge will sit at around 1.4v a cell doing a max of 16.8 and the hardware is rated just over that too. But like I said I'm still waiting for the ESC for the real test and will post the results...I am supposed to get the MM tomorrow.

IT WORKS! I got everything set up and sure enough 5s A123 is working great. I have to do some more specific test but it was starting up with the input all the way up at 17.5v. Thanks guys for the help. Now I got to find some diff replacements because I burned mine up in the first 40 minutes of running.

Excellent news! Apart from the diffs- use the FLM alu cups and mod'd ring gear with 3mm screws, other wise you'll be looking at FLM hybrids & 1/8 HB diffs.

Well I got the UE 7.5 diff kit but for stock traxxas gears, metal cup, and will mod a traxxas gear my self. Hopefully that will hold up better. I also plan to turn up the punch control despite the stronger rear end, I just want this one to last as long as possible.