How to install a guy wire kit?
The reason you need guy wire is to support the mast place strap at the top of the mast then extend the wire behind the mast so when you pull the wire tight you look down the wire and the pole and mast line up with each other. I like my anchor into the roof to be as high as possible because higher up on the roof there is less water and leaves to hang up as they go down. Next is to find a rafter to screw into I usually use 1/4 x3” lag bolts and that is plenty for a 40’-60’ span the normal range I see houses set back from the lines.
When I was an apprentice I was taught to site to the top of the transformer to the top of the mast and put my anchor in on that line but many times that did not end up on a rafter and that angle really did not help as much as a longer run. With a longer run of wire or cable usually you will cross a rafter and that is just right because the rafters are the strong points in your roof.