I think the slug plugs are illegal for IDPA SSP division.
Nope, as long as they are plastic. They are specifically addressed in the rule book.
I think I need to disagree with Brit's (most respectfully since I think I shoot with him occasionally) recommendations on the night sights. I find that night sights aren't as visible in the daylight as fiber optics are. FOs show up like laser dots in the daylight...you can't
It's then a toss up on whether you want FO sights on the rear as well as the front. Some (including me) don't like rear FOs or even colored dots because it takes away the natural drawing of the eye to the front sight.
I've heard others talk about a shorter-barreled gun, but I still prefer a longer one. I like the increased shot precision that the longer barrel provides. And for me, I'm strong enough to provide the increased inertia necessary to move an 1" longer barrel.
Glock 34s tend to rule in SSP, but I think that the M&P Pro shoiuld be able to hold its own in the division. It just isn't as easy to work on yourself as the Glock is.