You should email ARC, I've had fast and helpful replies from its owner when I've had questions.
HOWEVER... being a nerd I long ago made up a spreadsheet for these calculations. With the NXS 56mm objective and a 64.5mm outer diameter of the bell (measured on a 3-15x56 NXS) you will need a 1.27" ring height to clear a continuous rail. The high model M10 rings are 1.26" high, so I think you will have to use the x-high rings, which are 1.42" high. EDIT: if you are running the handguard without a top rail, and there is more than 0.02" gap between the top of the receiver rail and the top of the handguard (I would guess it will be closer to 0.15") then you may be able to use the 1.26" high rings. Not sure though. Again, I would contact ARC as the owner is very friendly and helpful.
If you instead had a 50mm objective you would be able to use the high 1.26" rings.