I had to make a 'double overlap' repair to my Zodiac Pro at the pointy end of one of the tubes, where there are three strips of material, one on top of the other lying at 90 deg angles to each other. It left me with a small gap where it was impossible to get a perfect seal, even though I used the proper Polymarine 2 part adhesive.
My solution was to use a product call Shoe-Goo
and plug the gap (unconventional in RIB repair but it works for the soles of shoes, so I gave it a go
). Six months later the tiny hole is still perfectly sealed and holding air. I've given the boat some pretty heavy use during this time and drive it hard (It's a 650 Pro w/150hp Yam) with no sign of failure.
Not sure if you can buy it in your country but it's available in the UK through Amazon and in the Bahamas, where I live. http://www.amazon.co.uk/Original-Sho.../dp/B000BQR55G