I've spent the past two months resealing and testing all bladder and strut valves on 04-06 slingshot fuels, diesels, octanes, and machines. I have also helped out with the same malfunction on some 06-07 flexi's. (two of the most quality companies in the biz in my opinions) the best solutions thus far to valve re-application has been krazy glue or an airtime replacement valve/bladder.
Krazy glue wont corrode the bladder materials and provided you do not leave cracks, folds, or creases in the bladder when applied, it should hold untill the kite see's its doomsday. Airtime has a new east coast warehouse/shop located in ft. lauderdale and specializes in the similar fixtures. Alex and Josh there are extremely talented and will fix any sort of kite to the point that it looks factory born. If your too lazy to do it your self check them out at
http://www.airtimekite.com/, or just go to the hardware store get the krazy stuff and be prepared to pull your hair out, its a standard side effect to hours of bladder work.
Not trying to pimp anything here just stating facts, marine grady epoxy's/ glues either don't stick adequately or corrode thin bladders.
(make sure to lightly sand area as well as wash with alcohol/water prior to application to ensure solid fixtures.)