Wow. This is very interesting, isn't it. A few thoughts. I have. regarding choosing a new saddle, bars or whatever, which may potentially "nullify" an existing fit, or not be "doable" with a scribe, piece of electrical tape whatever - if you can't get this then you just aren't anal enough. A good piece of cord, a yardstick, an "angle measurer" (I forget the official name) and a piece of paper and a pencil and you can add/delete any piece of equipment and replace it with any other. I've swapped saddles twice without any impact - took me over an hour each time, but that's b/c I am so friggin anal that I took like 15 measurements, repeated them, then installed the new hardware and repeated. While tom is correct that 3 people will see 75.1 cm as very different from person to person I know exactly what and where I am measuring so that is not an issue.
Now, as for fit and numbers - the same thing largely holds. When you get the bike home, measure the crap out of it. With the right tools and lots of patience you can get all your measurements and have more than enough to go off of to reconstruct the bike from scratch if need be. If you are careful in your measurements and constistent then it should never be a problem. As for the process, I personally don't really care. I want to be a good triathlete - not a good bike fitter. If I wanted to be a bike fitter I'd go to Serotta school and FIST and read all Dan's articles 10 times and all that Frankly, I've got enough to worry about trying to go under 10 for an IM - I couldn't give a shit about how Tom arrives at my fit - so long as it does in fact fit and makes me faster. That probably puts me in the minority around here, but I am just not interested in how we get to the result so long as we get there. For example, I make my living designing and building software. Part of that process is that there is a certain amount of intellectual property involved and the client doesn't get to see what is behind the curtain (and most frankly do not want to - they just want a functional product). Now, once the software is delivered the client "owns" that software - they can even look at the code if they want to. BUT - they certainly don't get an explanation from me of what the code does, how it was built, what the process was, and so on. If they want that, there are perfectly good places to go and learn that. AND, if they want to try to reverse engineer it, they are welcome to try but I do not guarantee the results. To me, this is exactly the same as where Tom is coming from. My LBS charges $75 on a new bike for a fitting - frankly, I think that is bullshit. Part of what I'm buying is fit, and it damned well better be in the price of the bike (note: I also do not haggle on price. I pay whatever is asked, no questions asked as I believe in the value of things such as the shop's expertise).
My take-away, is if you really want to know the process and understand fit, then you are better off going with (i.e. paying) a consultant like Fitwerx or whomever and hiring them to measure you, spec some bikes, then you buy the bike from a dealer, then go back to your consultant and do the final fit.
"To give less than your best is to sacrifice the gift." - Pre MattMizenko.com