Hi Darren
all the responses on treating your frame are correct, as you can see there is a considerable breadth of opinion. Your pauwlonia wont rot as a consequence of a quick drenching, but if you leave the boat exposed to the elements and half full of water in your backyard it wont take long to rot. My approach to the stringers has been to give them a quick coat of oil before I skin the boat, and I have used cheap pine with no rot to date (3 years). If you use cheap ply rather than marine ply I think a coat of epoxy or an outdoor paint after assembly is worthwhile. The real key to preventing rot is however storage, keep your boat out of the weather and make sure there it is not full of water when you store it and it will last quite a few years.
As for the skin, I have used PVC fabric on 4 of Tom's boats, it is easy to use, very tough and does not need any other coating. If you are looking for glue for PVC fabric in Australia you wont find Mauritzon but you can get 'PVC fabric glue' made by a French company called Ferrari. Ask you local foam shop, about $50 a litre.
cheers
David