Alright, got a question for the more experienced styrene-benders out there.
I made the tubes for my engines last night. I cut some rectangles of sheet styrene (.01? I think) to the right size rectangle, leaving a little overlap. Heated up the styrene under my work lamp, wrapped it around the barrel of a thick pen, and glued the seam. Because I was working with thin sheet I repeated the process, starting the end of the second sheet where the seam from the first wrap ended. The second layer I glued all the way around as I was wrapping it to make sure there weren't any gaps.
Well, they're tube-ish, but not round enough for my liking. I'm thinking of picking up a piece of wooden dowling as close to the right size as I can, then wrapping a layer around that, keeping the dowel inside the tube to hold its shape. I'd have to leave a little overhang on either end.
Any other ideas?
Oh, a little note. While I was rolling tubes (with my puzzled wife watching from the couch) I spilled probably 1/3 of a bottle of Tamiya thin cement on the cutting mat. Good news, it stayed on the mat, thereby saving me from re-finishing a kitchen table. Bad news, does that 
ever stink up a house when you let it loose like that! It also removes the cutting line grid, if you're interested!! 