Dwg 1 of my DE plans show most all horizontal dimensions reverenced from the tail post (0"). The Sta 2 cluster on the bottom of the fuselage is at 141". The cluster just above it, at the instrument panel area, is at 142" (which is 1" forward from the bottom cluster). There is a note "SEE 4" pointing at a tube from the lowest cluster to the instrument panel area cluster. The top of this tube is 1" forward of the bottom of the tube. So, it is not perpendicular. (Personally, I don't know why that is the case, should be no problem if perpendicular. I suspect that the prototype fuselage was built, then measurements were made for the drawing). Finally, the top cluster, where the wing front attachment is, is shown as 140". Note - my drawings are dated "CORRECTD - 8-04 LEM".