IMHO: Alas, I wish we all could be average dimensioned. Take me for example. 5' 10". Pretty average height. But I wear a 34-35" sleeve, XL gloves, 13 US shoes, 46R suit jacket, 34" waist, 32 3/4"stand over. Long torso, average leg length.

Thus my road bikes reflect that. I ride 55-58 frames. On my Colnago (55) the seat is way back, the stem is long (120 mm) and low in the hoods or drops my elbows are 70-90 degrees bent. My Motobecane and Centurion are 58, with shorter stems (50mm) average seat position, but with long feet and a toe down riding position my seat height on all bikes of 35" is completely out of sync with stand over (seat height: from pedal axle C/L to seat top in-line with seat post).

What I discovered is the greatest determinate of bike riding comfort and "fit" is flexibility. As long as I keep my calf muscles, hamstrings, hips, back muscles/tendons stretched and flexible, riding these bikes is easy but the minute I get lazy on flexibility, everything changes as with tight muscles/tendons/ligaments you essentially "get shorter" and aren't comfortable on a bike that...by the numbers, should "fit you". I would certainly engage in a lot of stretching and flexibility exercises a month before a fit and stay that way as long as you have that "perfectly fitted" bike.