We were getting ready to send a 75 RM125 tank out for reconditioning and paint. Because it still had the original black with silver outline decals on it, I decided to take some measurements to ensure repros could be positioned correctly once painted. See the below pics for measurement.
Measurements from the rear of the tank are taken from the edge of the seam (not the mounting eyelet). You'll note that the decals on the right side are slightly more forward. You'll also notice the rearmost portion of the decal on the left side is 1/8" lower, while the frontmost portion is the same height. Vertical measurements are taken from the table with the tank resting flat (no petcock installed).