I went to the sled show in the Twin Cities today and figured out why the wedge bad isn't listed as compatible with the ProClimbs. The ProClimb and the ProCross, which the bag is compatible with, have a vastly different tunnel. The ProClimb is heavily ported behind the seat, whereas the ProCross is beefier looking. If you look at pictures of the M1100T Sno Pro LE you can see the porting I'm referring to. In any case, the porting in the tunnel exposes what appear to be cooling channels (4 in X 1/4 in aluminum peices that run the length of the tunnel.) These cooling channels lead to the rear heat exchanger.
The wedge bag I was referring to uses riveted studs to attach to the sled. Two up front on the side of the tunnel, which the straps going form the front of the bag attach to, and two in the top of the tunnel that the bag slides into. The issue is that the studs for the back of the bag would be in the cooling channels that you can see through the porting. That being said, the wedge bag will work just fine as long as you just use Velcro instead of the rear studs that I assume come with the bag. My Boss seat on my Edge RMK is attached with Velcro, so it should stay on no problem.
As for the difference between the ProCross and the ProClimb seats, it's all above the fuel tank. The bottom part of the seat is all tank, and it seems to be identical between the two. The wedge bag's height only goes as high as the exposed part of the fuel tank, so although it may look like there's less room under the ProClimb seat for a bag, the part of the seat that the wedge bag snugs up against is the tank, which is identical between the two. The ProClimb seat is simply shorter, so more of the wedge bag extends past the back edge of the seat.