I have in fact done hundreds of shotgun patterns if not a couple thousand. On steel plates, cardboard and butcher paper. Over an expanded steel backer on steel posts, on a cardboard backer on wood posts.
Butcher paper/packing paper etc. done on an expanded steel backer is the easiest way. It would also be substantially lighter than a plate you can actually pattern large shot on.
I accept you don't like the easy or simple way all that often. :D
I think you mean "tumblers"
The shell you buy, the gun you shoot, the size of the bore or the clerk at the store telling you what you should do doesn't determine your actions, ethics or ability.