Quarter and Sheet Panels Installation Advice

You want to line everything up before fully welding anything in. Trunk extensions, wheelhouse, quarters need to be dry run for fit.
Keep in mind that most of the factory panels have alignment holes or notches to help get everything in the right place. AMD panels usually have these keys in them but cheaper panels usually dont. Even if they do, dont trust them 100 percent.
I dont recommend "all metal", use Evercoat Metal 2 Metal. Its a much better product.
As far as loading the vehicle, totally not necessary in my opinion. However, see what others might say on the subject.