Welcome aboard Sarel!
Your roll up PVC? Does that hang on the external walls, or approx a meter in from the existing shared wall?
I don't put water in my hobby car either (79 SB Cabriolet)..... heck, as I re-furb'd the rascal, half the boxes came from S Africa! Fenders, running boards, carpet kit, etc.......
fwiw - if you go up towards the top of the page, click on "Community", there will be a drop down box. Select "Social Groups" and a fresh page will open up. In there we have an Air-Cooled VW section. Gets a little activity now and then (nothing like a Samba), and the guys and gals would LOVE to see your projects.