Works very well. FRP is a very popular liner choice among monitor keepers. Reptile Gardens has their Komodo Dragon cage lined with it and it's still holding up after several years. FRP is probably the most durable of the wall/shower liners but anything rated for such use should be fine.
My only advice would be to take cage cutting it and to make sure you use the right adhesive. If it has any fiberglass in it you want to be very careful about dust.
Regarding adhesive, is there a lot of old adhesive on the back? If so you may need to use a thicker product to make up for all of the irregularities on the back.
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Currently keeping a small collection of various Gonyosoma. Both G. janseni and G. oxycephala.