John, the link you gave is for the "Spar-fly" which is different from the one I have (and that also uses the mount shown).
Also, in passing, there seem to be curious spirits involved in sailing:
Spar-Fly is unaffected by angel of heel.
I had the one shown here:
http://www.fisheriessupply.com/davis-instruments-windex-10-windvane-components and at the time it came with that mount. Later, I had to replace it, and the replacement came with a different mount. I found it easy enough to file the bottom part of stem so it fit the rectangular slot on the old mount and that's what I've been using since.
I like the little tabs. Upwind you want to keep the tail of the vane lined up with one of them to know you are close-hauled (after which you fine tune things using the tell-tales on your jib). Downwind, if the tip is between the tails you know you are in the zone for running wing on wing, but also that an accidental gybe is in the cards. I find the other style much harder to read.
The newer ones have reflexive tape on the tabs and indicator, for night sailing. Point a small flashlight up to get a quick read without ruining your night vision.