The templates are designed for A4 paper (not 8.5 x 11), so choose the A4 setting on your printer. (Even if you don’t have A4 paper.) After printing, double check the dimensions with a ruler.
We are still rather "boutique" in the U.S, but there are an increasing number of shops where you can get Hagan bindings mounted. Shops that have the Hagan mounting jig and links to the mounting templates are here.
I try to keep this list current, so if you learn of and are happy with another shop that mounts Hagan bindings, please let me know so I can add them.