@andabout, been thinking about your van life questions.
I think the best advice we can give is that you start with a FLAT base for the floor. So sweep the van out, put de-ruster down, and lay some foilboard or some kind of thin insulation down. Then put a sheet of 12mm ply down. Then, do the same to the walls - a foil backed insulative board, and a thin layer of ply. I can send you photos of what that looks like... contact me on Discord. Seriously, create the foundation before you put anything else in. Its' some work but makes all the difference.
Thank you so so so so much! I definitely will do my best to get the foundation right.. I will find you on discord and get in touch ♥♥