Can someone who has built there own custom trunk box let me know the dimensions of the wood I'll need?

What fabric works best and how do you connect the wood for a tight fit?

Any ideas from those who have do this?

I'm planning the same thing and asked around.
Usually the panels are form-fit, or snug-fit to each other. Not attached to anything.

I suppose if you take your tape measure and do some initial measuring around the trunk, you'll get an idea how much wood you'll need. I'm going to use 1/4" Luan. It seems to be stronger at thinner dimensions than regular plywood, and it takes glue nicely. It also keeps the panels lighter.
I was just going to upholstery glue foam to the panels and then figure out what I want to cover them with.... probably vinyl.

It'll take some trial & error on the fitment part..... buy extra wood!