Regarding 90s hybrids (Multitrack/Crossroads), the fit is more MTB like with longer top tubes and slightly sloping top tubes. For example, a 21" (54cm) Trek 750 has a 570mm top tube. I used bikegeocalc.com to match my position to my 55.5cm top tube cyclocross bike.

At 5-10, I went with a 21" Multitrack 750 for my drop bar conversion