A couple of years ago, Jim Rackham offered his solution to loading smoothbores, and its still the best answer to loading shotguns with chokes up front.
He suggests taking ONLY OS cards out. He uses an awl to poke an off-center hole in the OS cards before going shooting, and takes NO OP wads, NO cushion wads for the gun. Only OS cards. He uses 4 OS cards instead of the OP wad and cushion wad usually recommended. He puts a ball or " dab " of lube between the 3rd and 4th OS cards and lets the seating of that 4th card squeeze the lube out across the full diameter of the cards. Then he loads his shot. In you case, go ahead and use that plastic wad column with your shot, IF YOU CAN GET IT PAST THE CHOKES! Then, after the shot is loaded, he recommends using 2 OS cards on top to make sure that the shot load will not shift in the bore. ( Think of it as using a locking nut on top of a holding nut on a bolt.) Patterns are excellent using this method, without the plastic cups. The cards are quickly pushed or fall out of the line of firing, so they don't disrupt the shot pattern.
I still lube the barrels after seating the shot and OS cards on top of the powder charge, and 4 OS cards. I want the lead to slide over the barrel, and not leave lead streaks on my barrel, and flats on the pellets, if possible. This adds pellets to the pattern. It also makes the barrel easy to clean. I don't bother with the dab of lube between the 3rd and 4th OS cards behind the shot.
If you want tighter patterns, try using Card Stock( Index cards!) to make some paper shot cups small enough to fit through those chokes. ( Use a "mandrill" to make the tubes, then fold one end over like you would a coin roll wrapper. Glue or tape the seams.)The length is matched to the quantity of shot you are shooting in them, and then a couple of slits are cut in the sides, at the top, to allow the sides of the cup to open up when the cup leaves the barrel and release the shot. The length of the cuts and the number of cuts will determine how long the shot is held, and, therefore, what kind of density of pattern you will get at a given range.
You can also add fillers to the shot, to protect the shot from being distorted on firing, and increase the density of the pattern. If you are shooting steel shot, this is not much of a concern.
The best natural "filler" I have heard about - but not yet tried-- is Jiffy Brand Corn Bread mix, a fine ground corn meal flour. Its only limitation is that it will absorb moisture in damp conditions. You can limit that in the field by using a piece of plastic ( ie. plastic wrap) under the OS cards that hold the shot and filler in the cup in the barrel when loading.( Put the plastic over the barrel, then push in your OS cards, and trim the plastic.) Using the plastic will create a barrier to letting the air out, so expect the load to " diesel " on you, but the air will come out along the sides of the plastic and cards, and you can eventually seat the group down on the shot.
Good Hunting. :hatsoff: