Replying to the material on boxes

about a month ago we decided to build a park in my backyard, me and 7 other skiers and boarders just went out one day and started clearing the wooods behind my house moving boulders, clearing leaves and knocking down a few huge ass trees, finally over winter break we finiished clearing the hill so now ive begun making the rails and hits for it, and weve built a 20 foot long box for beginners and for learning spins into rails. the box is made and i just wanted 2 know what i should use on the box as a sliding surface, i was considering two pieces of metal piping but it would prevent you from buttering on the rail and the snowboarders wouldnt be able to 50/50 and you wouldnt b able 2 press so what should i use as the sliding surface on this thing. any advice is appreciated
Ski New Jersey