I've used ankle carry extensively over the past 17 years. The only rig that works for me is the Alessi ankle holster. Very comfortable (for an ankle rig) and after a couple of weeks, you'll stop looking like you've just come from the "Ministry of Silly Walks" (Forgive the Monty Python reference).
Unless you're a pretty big guy, I would also think the M&P Compact is too bulky for ankle carry. I could be wrong, and I know for a fact that Alessi has made a large number of ankle holsters to carry the Sig P239 for a government agency. Having owned one of those, I would think they're too big, but obviously it's working.