To me standover height is not relevant because if you buy your frames on the basis of top tube c-c length it automatically takes into consideration various tube diameters. If a tube is 1 inch diameter or 3 inch diameter (extreme hypothetical) the position of the seat post and stem quill will still be exactly the same for given frame angles. It doesn't matter how the quoted seat tube measurement is given c-t, c-c, center to virtual top or center to virtual center, as long as the person measuring the seat tube tells you how he arrived at the measurement. Some 54 c-c top tubes come with 54 c-c seat tubes - some with 54.5 seat tubes and some with 55, but I never had a top tube c-c real or virtual measurement throw me for a loop. If I know that one measurement the bike will fit assuming it is a road bike and not a mountain bike or a city bike. A bike should be sized for your spine unless you have very short or long legs (relative) in which case you should probably be getting a custom bike. Standover height shouldn't even enter into the equation because one can always stand over the bike with it held slightly at an angle if it has a particular high bottom bracket. Buying a bike for standover height is kind of like setting saddle height based on whether or not your feet can still touch the ground while sitting on the saddle.
Garth Libre in Miami Fl. USA