55 gallon Stainless Steel Drum

[filmtech]

Hey Guys!! I've been looking at re-doing my still and have a friend with a 55 gallon Stainless Steel Drum previously used for maple syrup. I have a 1.5" copper pot still setup sitting on top of a 10 gallon brew kettle. I'm doing multiple 5 gallon runs in the current still and would love to combine them to on bigger run. I also want something that's a little easier/quicker to setup and run... ie, leave the still built and just fill the drum from the top 3/4" NTP and empty the backset from a drain on the bottom/side. No more dealing with setup/tear down or flour paste.

First question: If I'm only filling the drum up with 15 or so gallons of mash, is that a bad thing. I know headroom is a good thing, but is there such thing as too much?

Second question: 1.5" copper seems to be fine for my 10 gallon still, but would it be ok on the 55 gallon drum? Cheap 2" is not easy to find in the South East! I know it would speed up the runs, but I don't mind taking my time and waiting for a good sittin/sippin drink.