I like your installation and your web site. A bit chilly up there, eh?
I'm not sure a roof mount would be allowed in my neighborhood - deed restrictions against anntennae and related gizmos. I don't want to push my luck and go through all that work only to have to remove it.
I'm basing my proposed installation on these guidelines from the Vantage Vue installation guide:
"Ideally, mount the ISS so that it is between 5’ (1.5 m) and 7’ (2.1 m) above the
ground in the middle of a gently sloping or flat, regularly mowed grassy or naturally
landscaped area that drains well when it rains."
You have followed the optional approach:
"You can also mount the ISS on the roof, between 5’ (1.5 m) and 7’ (2.1 m) above the roof surface. For areas
with average maximum yearly snow depths over 3’ (0.9 m), mount the ISS at least
2’ (0.6 m) above this depth."