i have an hdpe topped wooden box, i have no coping on the sides and i did hook my ski several times and made some cuts in the hdpe, then i took a coarse file and made 45° edges allthe way along the box and didn't catch an edge ever since ( i also rounded the edges on my beater skis with an angle grinder)
i don't think you need metal coping, but if you do make it, you'll need to use rounded metal pipes (or something similar) and put it between the hdpe sheet and your box base with metal attachment lips.
align the tubes so they're about a 0.5-1cm lower then the hdpe surface so your skis don't actually touch the metal when sliding flat ...
(i hope this makes sense to you ...)
Belgium represent !
Once You drop in, it's all "Hakuna Matata" !
"The windows are vertical how am i going to poop on those?"-Killabees
"God isn't black, you fucking moron!"-Shibby
"I shit rainbows and sneeze glitter."-Arabian