Moving the bag, or moving the mast, increases the potential maximum RM, the RM and HM are always equal and opposite. Without the wind in the sails the boat simply heels until the centre of Gravity and Centre of Bouyancy line up agian.

Try this series of articles, http://woodsdesignssailingcatamarans.com/indexstart.html

It talks about HM and RM and why Hobie Cats can fly a hull safely yet narrow cruising catamarans cannot.