At any rate, too little time went between my awareness of the bird and the time it took him to fly up to the neighboring roof. What I was most aware of was the hawk's wingspan - I don't think it was my imagination that made it look like 40".
I looked up information about red-shouldered hawks (University of Michigan and Cornell) and they are described with 37-44" wingspans. I'm glad I had enough time to take his picture before he flew away. Since these hawks are solitary and territorial, I'm assuming this is the same bird we were so surprised to see this summer.
Thank goodness Bob is as huge as he is. He didn't need to be hiding in the tree, but I'm glad he was!