I had never thought of all the uses of linex, but while I was there, a guy brought in a plywood tank, linex inside, use it has a livewell for stocking fish in ponds. He had tried Gel coat for boats, fiberglass, still leaked. LineX fixed it right up.
(I hate posting from my phone, stupid fat fingers)
As for tearing on plastic, the owner told me that you can use a plastic specific epoxy, he showed me some stuff they had, it was an industrial kind of stuff,two part, kind of melts the plastic, and bonds to the LineX really well. I need to find out where to get it, I will let you know. May be an option pending what you come up with, or maybe better for patching tears?