I also spent a lot of time thinking (too much, like normal

) about this instead of doing it. What I ended up doing was using a piece of scrap (read that as a piece I'd previously screwed up) 1/4" tubing to make a mock-up of the bends lengths (marked w/ a felt tip marker).
I could bend this mock up all I wanted to get what I needed; then use it as a pattern for the final tubing. It worked well and generally I only had minor adjustments for the final fit.
I used that same piece of tubing for all my tubing runs, regardless of size. Its been bent a zillion times and, while not 'flight safe', it has a place in my toolbox.
BTW, a set of crow's foot wrenches on the end of a 14" socket extension made tightening the fitting easier too!
H