Have to agree with most of the posters that this varies much more than your height. Not only your inseam, but how you tend to sit (how much you slouch when at rest). At 6' 0" with a 34" inseam I have no trouble technically "fitting" in a 30" seat in that I can set my feet flat on the floor and legs are extended straight if I sit erect. I find psychological space restrictions from being next to strangers and lack of variety of positions in which I fit to be the most uncomfortable things about Y, so I more or less avoid it for anything over an hour or two.