A quick learner from Michigan says:
November 3, 2014
This spline appeared to fit my storm window, but fell out after a few months when I tried using rubber cement to hold it in place. What adhesive and technique do you recommend for small projects? I also tried silicone, but it is tricky to apply. There are also products like CR205GL, but I have only a few windows to do.
Dave from SWISCO responded:
November 5, 2014
Actually, the adhesive is used to cement the glass to the storm window frame. The glazing spline just fits on top of the glass. If should hold securely into the lip/groove of the storm sash. That said, using a little bit of rubber cement to help secure it can't hurt. It's possible you need a thicker a glazing vinyl.