I would think the easiest thing to do would be to just take the 4-foot wide rolls, and make 4x5 sections, covering 2 frame bays each. Then it would be much easier to drop a section in the future for access/repairs, etc. Or am I missing something?
Are you going to try to over lap on the cross members or run a seam length wise.
I've built a new frame and plan on butt joints at my 48" cross members with a 2" strip to cover the butt joint and to secure the panels. I went with 12' material so I would end up with scrap that is 2'x4 versus 1'x4'