I have a M2 mounted in a ARMS #35QD mount with medium height rings. The scope was a bit bigger than I anticipated, but it isn't a problem for me at least. Works well mounted to a flattop. If you don't like the rubber scope covers, they can be replaced with butler creek #03A scope covers (33 mm diameter). The scope has pretty good eye relief on paper, but the rear lense is located about a inch into the scope tube, so that there is only about a 1.5 inches of useable eye relief. If you don't have a good cheek weld, and your not using the rubber eye piece, the tube will make contact with your face.
The only other issue I have with the scope is that the zeroing procedure can be a pain. There are no discernable clicks when adjusting the windage and elevation, which makes the process a bit hit or miss. Best advice I can give, is pay very close attention to what you are doing when adjusting the scope, its easy to lose track of where you were and what direction you need to turn the turret since there is no markings for up and down or left and right. You can save yourself some time by taking a pencil and writing on the turrets directions for adjustment as well as making reference marks.
As for the ARMS mount, absolutely love it. Offers a lot of flexibility and the medium rings put the scope at proper height. To be specific I did some comparison measuring of the distance from the flat top to the point of aim for a detachable carry handle, aimpoint M2 in a railgrabber mount with spacer, and the IOR M2 in the ARMS mount. The distances were measure with a ruler, so I could be off about a milimeter.
Carry handle - 36mm
Aimpoint - 39mm
M2 - 40mm
With the scope mounted at this height, I could not see any shadow from the front sight whatsoever, under multiple different lighting conditions. From what I have read, the armalite mount will put the scope in the same height range as the ARMS mount.
In addition, the medium rings consist of the low height rings with spacer. The spacer just so happens to be the same thickness as the spacer on my railgrabber mount for the aimpoint. This means that if I were to ever get a SIR, I could just remove the spacers for the rings, and the scope would still be mounted at the proper height. One caveat to this though, at least as far as the IOR M2 is concerned, is that the housing for the illumination switch will interfere with the mount base if only the low rings are used. It's just barely makes contact though, so if you really wanted to use the low rings only, you could probably reduce the housing wall thickness and everything would fit fine. But that would require grinding on the scope which may cause some consernation.
Edited to add that instead of grinding on the scope, a small amount could be ground off the side of the mount base to allow for clearance, which would probably be a much better alternative, although it would still lead to grinding. Ideally, if one was mounting on a SIR, the ARMS #22 rings would probably be a better choice although you would lose the one-piece mount advantage.