Interesting thread here. I never realised that there were so many differing styles and designs.
Just had a squint at the tiny pics of the racks on John Worrall's Heart of England site, and it seems there are differing heights of non-sidescreen carrying racks. I'm guessing this is to give the option of clearing the 'cyclops' third rear brake light, but it also means the luggage support loop part of the rack sticks rearwards beyond the over-riders I think.
Maybe it's time for a few photo's of TMers racks..? I've Googled them but they don't always give the information needed with them.
Or maybe I'm just a saddo..??