ARC CDG in a MDT XRS?

It should work, but I haven’t verified personally. You should email MDT and/or ARC. The CDG inlet is essentially rem700, you just need room for the trigger hanger. MDT is usually pretty good about leaving clearance in their inlets for hangers. The CDG was designed to work when using AW mags with the normal AICS mag catch, which should also be OK with the XRS. If you want to run AICS mags, you’ll need a different mag catch.