Nothing about that looks acceptable. I would never, never butt join pieces where any type of load is expected and would never accept replacing requested material with " ordered the wrong" material. Especially with a different size.
And the tack welds look hideous. If it's not TIG it's wrong...
Depends on age (yours) and financial ability.
Is this "the last rig build" you'll do? (Age question)
Can you afford to start from scratch? (Financial question)
My $.02 is sell and get what you want/need to travel as you wish.
The FRP directly over the exterior should work fine without any real extra effort.
I think as long as it's sealed at all corners and seams it would be waterproof and hold up well. What method of adhering are you considering, screws, bonding adhesive.......... ?
FRP/Filon board is absolutely the best way to proceed. Way less labor intensive and more cost effective.
To save it, you need to remove the Raptor Liner and seal the wood. Or replace the wood.
Raptor Liner is made for solid surfaces, which sealing would accomplish. Expanding and contracting wood separate the material and let's the wood delaminate, which is very evident in the pictures. Use a...
I so wish I could take the whole rig off your hands. It's darn near exactly what the Wife and I have been looking at. I'm near retirement, about a year and a half away, and would love this combination of truck and trailer.
If I could wheel and deal, sneak, bum, borrow or beg the Wife to take a...
I use headlamps and a good rechargable led flashlight. I use solar glow sticks as nightlites.
I really don't like using lights that require a battery, headlamps as an exception because of how long they last.