I took my 19' FD sailboat to a lake in Az. in mid summer, it lost 15lbs of water wieght with out doing any thing. It was a balsa core glass boat. I kept the boat about a mile from the ocean under a Vivatex cover. Maybe you could put some tape over the bad spots and fix them after you go up to Mono Lake. The East side of the Sierra's can be hot and dry sometimes.
I can't remember where but I saw a place selling clear Duct Tape, anyone used it?
Don