I thought about using Marine grade - but as I understand it the glues are pretty much the same as CTX - what I did do was epoxy around the edges and then Varithaned the rest.
Anyway, as I said super nice job - I love seeing these trailers brought back for a new life - AND they they are being used and enjoyed - which it seems you are doing
1956 Flying Cloud
Four Corners Unit
Albuquerque National Balloon Fiesta
Vintage Trailer Academy - Formerly the original