Well, I went with 7 inches of clearance for the pipe, and used heavy gauge steel flashing through the roof. The stove (or stovace) manual calls for 4 inches clearance in a "corner" install, I have 18 inches. I went ahead and left the steel plenum, or air jacket, that I built and mounted one of the blowers from the DAKA so I'm able to blow warm air across the shop. Originally I planned to set the stove on blocks but after some measuring I didn't. Those pipe sections were 4 feet, and with the stove directly on the floor three sections put the top right close to 2 feet above the peak... with only about 5 feet exposed to the outdoors.
OK, so I didn't use class A chimney through the roof... but I do plan on keeping the thing clean. Just 12 feet of double-wall pipe, straight up, should draft one-heck-of-a-lot better than the single-wall out the window did for the barrel. The high-temp silicone at the flashing should be cured tonight when I get home... maybe a test fire??