Motorcycle Repair: rocker box leak, rear cylinder, gasket

Question
1993 FLSTF. rear cylinder is leaking. it has been for awhile. how can i tell if the leak is between the upper and middle box or if it is between the lower box and the heads. i am no mechanic, so do you normally replace all gaskets (even the lower one) or just the upper and middle ones if the lower one is not leaking? i have a repair manual and i think i can do this repair. the upper and middle box repair seems simple, lower box another story.

Answer
Usually your leak is between the lower box and the head. Since you have to tear it apart, you need to replace all the gasket anyway. If it were me, while you have it torn apart, I would do both the front and rear. You dont want to do one cylinder and 6 months later do the other one because it started leaking.
Good luck and happy riding
Mike