Touch your toes? I actually haven't heard of a real standard.

This is mine from the start of the season, I've since flipped the stem which probably dropped it another .5-.75 on an inch, nothing major though. Its still higher then my track bike and I ride that in the drops but the track has shorter cranks that keep the knees from hitting the gut and only have to maintain the position for 4000 meters at most. The race I ride the hoods and can comfortably do so for 3-4 hours. There is a limit of how much stack height you can have with a carbon steerer tube, usually 1.5" for a 1 1/8 steerer so there is that.