I know...BPs just don't have the right body shape for skilled climbing. And those plastic hides generally offer no traction at all. When I had a large BCI for many years, I got tired of watching her unable to use or enjoy the top of her very large plastic hide, so I built her one that was flat on top & nearly as wide as her enclosure so there was no place to slip off to, & I used a carpet mat (the kind with non-slip rubber backing) on top of her hide- that was a real success! She used it all the time, & with confidence...that looped carpet mat was great traction (& it was also washable), & she clearly loved basking on top of her hide.
If you do add a rod of some kind, keep in mind PVC is "practical" but very slippery too. Branches are preferred for texture, or you can add texture to wood dowels. (I've seen them wrapped with rope, for example)