We don't know how much guys of the past that were really tall would touch - Larry Nance, Shawn Kemp for example. LeBron at his best athletic ability. James White. Vince in his athletic prime (~1999-2001).
You think windmills are so easy? You have to rotate your arm very powerfully and quickly in that split second that you're in air. It's not as you think it is.
Go to a lower rim that would give you his reach and try windmills, film them too.