From what I've been reading it seems that you can get a good "fit" from a frame geometry that is compact (and therefore maybe a bit smaller than traditional frames) by adjusting the stem length/height and the saddle position/height. Of course, the frame size still has to be within "the ballpark." I know that is the theory of compact frame manufacturers and although I'm not endorsing this theory, it does seem to make some sense. The exception(s) would be if the frame was either too large (making these adjustments impossible) or grossly too small, placing the center of gravity somewhere it shouldn't be which can have an effect on weight distribution and/or rake and trail which affects handling.