Coping small diameter to side of large diameter cylinder

[Scotsman1886]

Ok,building a smoker out of an old compressor tank. Plan is to put the "chimney" of 2" pipe vertically on the top side of the back of the horizontal tank. If that makes sence. If I put it on the top, it would be an easy cope but I want to put it about a quarter the way down the back.

Any layout ideas? I had thought I would hold it in place and run my dividers around to give me a line. I was thinking there has to be a better way.