I just made and uploaded a rig to Rig Exchange of my Marshall DSL40C. I used my Helix in the signal and put the Helix "Clawthorn" drive in front which is a model of a "Wounded Paw Battering Ram" bass overdrive.
If you're interested, check it out - search for "MARS DSL40C CLAW" or Author BSD.
Hope you like it! Feedback welcome.