unfortunately, yes.
I called many places to get lexan or HDPE, and the guy I spoke to said that HDPE would slide better than lexan.  It gets a little slow, nothing that a little water won't help speed up.  Not a big deal.  But as far as catching edges.  You have to have completely detuned edges for my box.  There are tons of little black plastic scrapings around my yard from plastic that's been shaven off the corners.  I would really making a coping on the side to prevent catcing edges and shaivng off the plastic.  Even if the coping is a few mm below the plastic, it will still work.  Otherwise, bevel down the edges of the plastic and your skis(underfoot).