Best way to attach this to side of van

[cuboid]

Previously there was some batten on the top underside screwed and glued to the wall ply. Is there a better way?

 

[cuboid]

Would this wood underneath prevent the bottom of ply getting wet? Screwed into ply with a repair thingee

 

[Tigercubrider]

Maybe some wood blocks glued to the van body and then the cover screwed to them? The wood blocks on the inside. Assuming that what we can see is an external panel. Not a second skin

 

[foxhole]

Baton works fine, if you want the bottom kept dry maybe a strip of plastic J trim on the bottom.

 

[cwhaley]

https://www.diynot.com/diy/threads/waterproofing-this-ply.501511/