1/8" HDPE is really thin but I was able to countersink it to my rail barely. On my box
I used 1/4" and it's so much more solid. But 1/8" is possible, just pretty sketch. Also 8' is short dude. I'd go with atleast 10' or
12'....or make 2 8' boxes like i did.s really think but I was able to countersink it to my rail. On my box I used 1/4" and it's so much more solid. But 1/8" is possible, just use coping i guess. Also 8' is short dude. I'd go with atleast 10' or 12'....or make 2 8' boxes like i did.