IIRC, they are supposed to attach to the front and back side torso's, regardless of the method (omni or magclamps), with 5 and 6 man teams adding the back and front center torso accordingly.
magclamp suits usually have the clamps on the front torso and knees of the suit (see the Fa-Shih), suggesting they'd normally hang like limpets off the mech. the marauder BA however doesn't show that, which suggests to me that maybe the clamps are on the back of the suit (and given its lack of hands for climbing, perhaps include some sort of winch system to left it up?)