My approach to bike fit is to first get the seat in the right position to locate my hips properly over the bottom bracket and cranks. (Sometimes this requires a seatpost with non-standard set-back.) Then I play with how much forward lean I want. (The compromise between comfort and wind resistance.) This locates my shoulders in space. Next is how much arm bend I want to ride with. Now I look at my arms as pivoting around my shoulders. This means my hands swing an arc. But for the small part of the arc that is of interest, ie where the handlebars should be, that arc closely approximates a line, a line that for me has a "slope" of 1 cm of headset spacer/1 cm of horizontal reach.

So I have now located that line in space and can define it as being located at one point in space X cms forward of the BB and Y cms above the BB. Anywhere on that line will give me the same back bend, shoulder location and arm bend. (The positions will not be identical, but over a 4' length of that line, very close in comfort and efficiency.)

This approach makes it possible to get a wide range of bikes to fit me well. Bars low and close (limit being my knees hitting them when I climb) or high and far forward. I pushed that aspect to the extreme on my old commuter which had a very high HT. Put a 180 mm stem on it. Got the shoulder position and comfort and it located my Zipper fairing far forward and high, a great place for it for Seattle winter commutes, often against winter storm winds.

Now what I am saying here IS NOT what anyone else's fit should be. That seat location and shoulder hence handlebar line still need to be determined. Once that is done, finding bikes that fit is just work with the bike specs. I draw the bikes on a CAD program where I have all my other bikes. I can the quickly see what seatpost I need to locate the seat and stem for the bars. (And see if the bike is feasible.) ( have also written programs and a spreadsheet to calculate stems and the weight distribution between the wheels.)

Ben