I am not sure you really want an MP on a 27.5 wheel MTB. Problem is that on slow steep uphills, the hub can't turn fast enough to produce much power. I have a 26" MTB with a rear MP5 and it bogs down on tight slow steep hills, and is not very agile. Works OK if you can keep your speed over 10 km/h, but can't always do that.
I also have two hybrid folders with 20" front SP5s. They work surprisingly well on hills despite lower power. But the 20' wheels spin faster at the hub and that makes the difference. Top speed on the flats of course is less.
