8ft box rail need some help
 

so i took a welding class this year from my highschools college program and i built a 8ft snowboard box rail and i'm wondering what is the best thickness and best plastic (hdpe) or whatever to buy, its all built and everything i just need to fill in the space between the two outside rails with some wood and the plastic on top any suggestions thanks.

was reading about making a box today, from what i was reading, trex (plastic decking material, can be bought at home depot/lowes) is made of hdpe and would work fine

ok cool if anyone has any other ideas let me know

i get HDPE from usplastics.com
its about $40 a sheet for 24X48X3/8 inches

UHMW PE is the best, HDPE is acceptable

1/4" at the absolute minimum

is UHMW about the same price as HDPE everyone says its so much better
I have HDPE on 5 boxes and rails and i love it. i cant say i have used UHMW though