I do all my big trucks outside. Always get stretch so I will align the panel best as I can, lay it down in the middle then start working on align the edge. Sometime it right on but most of the time I have to let the vinyl stay puckered like rolling waves with it hitting aliment on certain spots.Using the heat gun I will blow heat under the vinyl and push it down in alignment, most of the time you are going to have to pull up the spots that pushed down to help get aligned.But that well shrink vinyl on edges just enough to line up.It might sound crazy, but it works for me and I get alot of stretch here in the summer, plus some panels will drive you up the wall. Never stretch the first panel on purpose, but going to try that. Sounds like that will work good.