car hauler decking suggestions?

I have just torn off all the rotted wood decking from my 19.5ft long flat-deck car hauler. The deck support crossmembers are about 2ft on center. I was thinking about using some composite decking instead, but few are manufactured 1.5" thick, less in 20ft lengths that would fit my existing trailer requirements. Also, I think I'd have to add more cross members between the existing crossmembers, because composites are not as rigid as wood. Anybody have any experience here?