One of the reasons I turn the van into a panel van was to gain extra storage inside. One strategy is to use the new wall space to store flexible stuff sacks and items that can be fastened to the panels.
I modified my wood templates and the fabricated replacements using the same black plastic material that Werksberg uses. These black plastic panels will be covered with fabric. Then i fitted some standard sized plastic rigid molle panels from https://greyman-tactical.com.
Molle panels can be fabric webbing, aluminum or plastic. They are modular and can accept soft bags as well as rigid inserts. Items are attached with special military style molle straps. The RIP-M panels are fastened to the steel van walls and welded in backer plates using nutserts.
I hope to do same with the rear hatch