HCA: Hermit Crab Association

I assume it is safe but would like to confirm that. I made a second level from a cut bin lid an some large suction cups (some as seen on tv product. All plastic) to hold it up. I also have some zip ties in the tank to attach the vines I'm using as a bridge for access to the second level.

Also to avoid making two posts I would like to ask if anybody has ideas of what I could use to allow my tennis ball sized crab access the second level? Currently only my small crabs can but even for them the vines are almost to skinny

Yes, plastic is fine

Maybe a branch would work for helping your big guy climb easier? Or a piece of cholla or cork. What kind of vines are you using? My large does okay climbing vines that have a lot of fake leaves for him to grab onto. I also try to group them together so there's more to grab.