Over the last 20 years I have done an almost blank slate refit on each new bike. I set the saddle position the same, but the bar height, stem length, and cleat position I did just from feel. Ride a few weeks, see what hurts, tweak, repeat. Then I compared my dimensions from 1993, and the biggest deviation was 3mm, in stem length, and that was probably because the hoods changed shape over the years. Even did a new pro fit recently, and all he did is move my cleat back about 2mm, but I could not feel the difference.