Ha. Whoops. Thanks for catching that.
Fearfeasog, in answer to your question, I've learnt mainly through trial and error what sizes I like to ride. Sometimes, a 21-inch/53 cm frame will fit, but sometimes, it just feels too cramped: top tube lengths vary. Unfortunately, however, 22-inch frames usually crowd me a bit in the crotch. This is where adjusting w/ stem lengths comes into play. You sound like you have a slightly longer inseam than I do, though, which gives you more options.
I've found the general rule-of-thumb works well for me as far as the top length: if I look down at the front wheel, the hub is not visible beneath my handlebars. When the hub is visible by anything more than about a cm, I tend to feel crowded when tucked into the drops. That's how I tend to gauge it. One of the pieces I've read about bicycle fit is at
http://www.peterwhitecycles.com/. He basically describes what kind of 'feel' factors one should look at as far as fit goes. And that's really the most important part--not numbers or measurements, but feel.
One thing that might render that Shogun unappealing, btw, is the seatpost--make sure it's not stuck into the seattube. If it is, realize you will have to kill yourself to get it out.