When any new pre-formed panel is used, Southern Kombi Parts like to first off, separate the parts by un-picking the welded joints, so that they can ensure they can treat every inside surface before fitting to ensure as much protection as they can without galvanising them.
The perfect example of why they do this was with the inner part of the lower valance. When it was taken apart to help to cut it to shape to fit the van, the inner surfaces were plain old bare metal (not good), which is often the case with reproduction panels, they are assembled and then given a thin spray treatment of primer, unfortunately, this does not reach all of the inside areas, which can result in them rusting from the inside out!
This is why they separate them first, make any adjustments required, and then cover everything in either Red Oxide primer (as it has a rust inhibitor in it) and possibly some gloss paint just for that little bit of extra protection.
Good practice, nice attention to detail and gives you that extra peace of mind that the job is done to last!