This!!!! I'm really annoyed with myself for not thinking of doing this because I use a very similar technique to pull rubber isolators through the frame of a quadcopter I have.
I didn't watch the video yet but what I did was take some kevlar thread that I looped around the valve ridge, pushed the valve as close to the hole as possible and then rotated the thread around the perimeter of the valve which pushed the strut hole material down into the valve ridge. On the quad I'm able to just pull the thread, which is tied around the isolator, and the isolator seats itself every time. Here the 90 degree angle and hardness of the valve made that seem too risky to try. Either way, the valve is now in place and the kite is inflated downstairs for an overnight air check. Thanks again to all for the help, especially direnc !