The problem with using thinner (less viscous) adhesives with this type of repair is that you are dependant on their ability to flow and remain in the required areas. Then again, that's the problem with less viscous adhesives from the beginning. They don't always remain where they are needed unless there is something behind them preventing an escaping flow. Sort of like filling a bucket. If it has a hole in the bottom it all flows away from the container. That's the big benefit of the urethanes. Although they also will flow away if the avenue exists, their increased viscousity and expansion rate tremendously assists in keeping the adhesive where it needs to be.