Yea I'm gonna have to get a cheap step stool.
As for the wash itself, we are having severe drought here in San Diego (CA in general). Not sure if they'll give me a ticket if I use a hose to wash a car, but I don't want to waste water anyway. So Optimum No Rinse Wash & Wax is on the way. I'll probably have to rinse the car before doing the actual wash though, but still water is saved compared to a fully traditional wash. I think with rinseless wash, if I try standing on the door step I might be able to reach and cover the whole roof since there's no water to make a mess.
By the way the vista roof on the Edge is magnificent.