Good advise above. I have three SLX frames, custom Davidson (from my goo fast years), Designer 84 CIOCC and a Tommasini Prestige, all with as close a fit to each other as I can get. All are 58cm but built with different intention, geometries and probably theories in addressing the customers needs. While I love the rides and have 60+ years on bikes I can't identify a meaningful difference in these frames, other than the Davidson does not sparkle like the Italians.