I would weigh the powder to make sure you have enough in there for the rifle to regulate.
I don't use a felt wad (it's a waste of space), the lube cookie is on top of the powder. The lube is sealed from the powder using a wafer wad of beeswax foundation wax. 3/16" lube should be plenty.
Two .030" hard card wads are under the bullet as scrapers - you'll need them about .425" diameter for the .400
Roscoe told me he only uses lube, and can't tell the difference from having wads as well ( and I hate to admit it, but he shoots nearly as well as me!)
Kynoch factory greasers are .410, and will obturate just fine to 418. My 450 No. 1 single using 1 in 15 bumps up .014" and shoots 3" groups at 100 yards. Make sure the alloy is lead/tin only.
I think the 330's will be too heavy for your double to regulate.
Remember, these rifles are hunting rifles. A rifle that shot 3-4" composite group at 100 yards in the 1880's was considered regulated. A .500 was called good at 6", probably because the regulator had had enough of the damn thing!
Use a standing rest if you can, I think using a modern bench rest can upset the apple cart with these things.
