I bought a 07 Novurania rib and it has a slow leak in front tube, I have replaced all 3 fill valves [C7] and was hoping this was the issue but it was not, have tried 2 times with soapy water solation to find leak but have not found it, maybe leak is where I cant get to part of tube next to hull, so what have you done to find difficult leaks and also how would tube seal/goop work and how do I get it on other side of front tube since it has 1 valve on 1 side only, the back tubes are solid no leaks.