Cargo Van Angles

So I need to do some work with a 2010 ford E-250 including striping. Im using some new templates that came with Omega 3.0. I bring it in and put a straight line on it only to find out the centerline of the van drops a lot, and I mean a lot the farther towards the hood you go. to the point where any straight lines of text in the computer look way off on the van. I understand that most cargo vans actually have cargo so they tend to sag in the back, but I've never worked with something that had such angles. Do you guys tend to follow the body line no matter where it goes or go against it so its level with the eye? I've done plenty of vehicles with stripes on vehicles with weird angles, this one just seems bad. Giving me a tough time.