The aft end is pretty easy to determine where the top and sides are. I drilled a hole and attached a hook. I tried hanging the paint with a drop of water in it to see where the front of the pant was. This only kinda worked.
I pushe the pant up against the wall thinking I could locate the most forward spot. This kinda worked. I submerged them in water thinking that would help me find the side lateral lines.
I settled on the top line first and then measured down the sides with a flexible tape measure to determine where the side lines should go. And at this point I noticed my wheel holes were centered, but will fix them later.