Sorry but "gripfill" is not the best adhesive you can get. "No more nails" and " gripfill" are pretty much the same. The problem they have is once you expell them from the tube they form a skin quite quickly, and the skin does not stick . I have found unibond "mega-gripp" and evostick "sticks like s**t" to out perform most gap-filling adhesives. Another item which although is not designed for but beats everything hands down is standard clear silicone.
Top-tip = Ensure that the walls and timber are dry and dust free, otherwise nothing will work.