Ok, I got the prehook to work like this:
Code:
ZO_PreHook(ZO_Stats, "InitializeKeybindButtons", function() self:SetupPosition() end)
I had tried using "stats" before, but I didn't do "STATS", so now I'm finding it in zgoo. I'm still researching how to index userdata, but at least I have something to index now.
At some point I'll get around to changing my setup function to add the control to the list so it auto-formats everything around it, but for now I have it working without over-writing any stock code, and it plays nicely with both Extended Stats and Soft Cap Info, so I think I'm going to just play the game for a while.
Thanks for the help, I'm sure at some point I'll be bugging you guys again with all my noob questions.
Edit:
The addon is uploaded
here, if anyone cares.