I own a 12 ga NewEnglander with the screw-in tubes. I've also shot several other ML shotguns and have to agree the best method (as Screwbolts described) is the V.M. Starr loading system of 2 card wads over the powder & 1 over the shot.
Unless you are using steel (or other hard non-toxic) shot there is no real need for a plastic wad. The Starr method has given me the most consistent patterns from several shotguns & chokes.
Here's a link to a story by V.M. Starr - http://home.insightbb.com/~bspen/starr.html