What thickness of Coroplast for enclosing TT underside?

I have not dropped/opened up under the trailer.
I have some kind of support/cross members for support to screw into.
My coroplast is held in place by self tapping screws.
You will have to cut around suspension and anything else already mounted on the frame.
I would consider taking measurements of where important items are in case you need access to them. Then you will know where to cut a hole.
Pat