The Cantz1007 was initially designed with a single vertical stabilizer , but was found to
have longitudinal instability , and so one of the first modifications was the twin tail structure.
Someone with better access and linguistic capability than myself could probably find
how many examples of each type ( single vert stab versus twin vert stabs ) were built.
I believe this to be a photo of the earlier single vert stab example of the Cantz1007.
I may well be wrong.
Kopfdorfer