I am getting ready to do the rear fuselage top skin on my 650.  I am a little confused by the drawings... at the longerons, they show 650mm from center of the rear-most bulkhead to the center of the middle bulkhead, 880mm from there to the center of the front bulkhead.  But - the drawings show 635mm and 840mm, respectively, at the center top. Being a parallelogram, with the indicated slant of the bulkheads is 84degrees, would not the measurements theoretically be exactly the same at the top as they are at the sides?  Or, am I missing something?    If I make it the stated measurement at the top, the forward bulkhead is nowhere near 84 degrees of slant, and looks asymmetrical.  The drawings appear to show all 3 bulkheads at the exact same angle of slant.

Any insight would be appreciated!!!

Brian M