^Yeah, you're right. I wanted to get an idea so I did some very rough trig calculations based on over-simplified assumptions (all I could go on really), and my result was a limit of 62.5m on Cogswell, or roughly 21 storeys at 3.05m(10ft)/storey, based on the Citadel couryard rule. If you're wondering, I used/interpreted data off a
topo map provided here and assumed an eye-level of roughly 3m below the top of the courtyard wall for a person standing at the opposite wall in a straight line (like I said, oversimplified). My raw data is probably also off, but I knew that initially and just wanted to get a rough idea.
Don't quote me on these figures though, like I said, it was horribly over-simplified and based on measurements off a map which is a cardinal sin!