I was wondering whether it really mattered if a yacht was a little overweight. I've taken the "Acceleration" page spreadsheet and produced a whole new version. It calculates drag and acceleration against a time line, rather than against a speed line (spreadsheet here, approx 96 kb), in order to yield relatively stable calculations. More importantly, it now factors in the yacht displacement in order to calculate acceleration, and calculates the distance travelled during acceleration. For a given wind speed and displacement, the sorts of results it gives are shown below, plotting speed and distance against time while reaching and while running. These particular graphs are for a wind speed of around "1", showing the yacht reaches maximum reaching speed after about "6" units of time. These are arbitrary units, because the spreadsheet is not calibrated. However, if you think "1 metre per second" for the wind speed, and "6 seconds" for the time, you'll not be too far out.