Brewer/Diffenderfer?

I am usually only a lurker here, but I was on the Big Island last week and in the lobby of the Kona Inn were a number of classic boards displayed on the wall. Among them, a balsa  Velzy/Jacobs pig, an original balsa  Quigg Malibu Chip, a Pacific Homes Systems plank, etc. Very cool boards. Anyway, in the display was a beautiful single fin chambered balsa gun, about 10' signed "Brewer/Diffenderfer". It appeared to be late 60s vintage. I lived on the North Shore in the late 60's, during the heyday of the mini-gun revolution. At that time Brewer and Diffenderfer were very big names in what was "cutting edge" designs of the time. However, I recall that they both shaped very independently from each other. I had no idea that they ever actually collaborated. Does anyone know more about this?