Not many draw backs at all, you will find that most Auminium Boat builders put poly tanks in there boats and so do a lot of the Fiberglass builders these days. They are all rated out of the factory and have very few problems, biggest thing you have to remember is they will expand and contract a little so the area you are putting it in just needs to be a little bigger only by about 10mm around the tank. Just use the black rubber fuel hose, it’s the best stuff for under the floors.