What about these to replace headlining with? and should it breathe?

[steve yates]

Steveeasy, is there a non glossy non reflective version of that? And do you think the flimsiness of the wickes cladding would matter? Is it going to be taking much punishment?

I'm guessing I could also just get marine ply cut into strips and then paint it whatever I like?

 

[Hydrozoan]

... I'm guessing I could also just get marine ply cut into strips and then paint it whatever I like?

If you are looking principally for a painted tongue and groove appearance, you might be able to rout part through a ply board to emulate it - subject of course to any curvature and fixing issues with board, which would be similar to those with vinyl-covered board.

 

[Quandary]

You do not need marine ply inside, any reasonable wbp grade will do the job unless you have a serious unattended leak. If you are leaving a shadow gap between the boards finnish birch makes nice sharp edges and has good smooth surfaces, pricier than some but worth it. The deck of my trailer is birch ply, I reversed it this year after 14 years of all year round exposure, the glue had not failed but it had been abused by loads of rubble.