so right now i have a PW 108mm symmetrical BB, but the lateness of the hour makes my head dizzy at math. For my new "ideal" chain line i'll need to add +9mm to the drive side (the left/non-drive side, i figure, can be symmetrical or asymmetrical, i don't care)---currently the chain line is 45mm, and i'll want a 54mm. however, in order to get a BB spindle of proper length for the +9, would i get:
1) a 117mm BB?
2) add +18mm (+9mm for each side) and get a 126mm BB? (That seems ridiculously long/wrong.)
3) get some kind of R+5, and take into account the 5mm (2.5mm could be added to the drive side at the present 45mm chain line measurement) of additional lateral movement in the cups (which would equal what)? A 116mm R+5? A 123 sym?
4) find some other length at complete random? (pick a number, any number)
5) or just ignore the problem, because 9mm of chain flex may not be ideal, but it won't make the Middle East crises any worse.

And yes, i want to keep it JIS square taper; and no, using loctite doesn't frighten me.