Joel and Matthias, I perhaps ungraciously pointed out that droop measurements in a Mini are for the most part irrelevant. There isn't anyone that I know who actually measures or attempts to quantify droop. We do have an interest in shock length, only because it tells us how much we are increasing or decreasing droop. Also we're probably only talking of, at max, a range of 2mm or less. If you check out Matthias's shock to axle ratio, you'll see that 1mm at the shock is much more at the wheel. No, I made no attempt to measure it.
Now, this next is going to get me into trouble with some. I generally run 56.5mm shocks in front, only cause at that length the spring retainer slides easily between the shock body and the lower coupler. The rears are no longer than 57.5mm and are usually 56.5 or 57mm. I've never found that changing shock lengths and consequently adjusting droop in the front ever made a damn bit of difference. Occasionally, changing to a slightly longer or shorter shock did have an effect for the rear. Please note the above may only be true for the smooth tracks in my experience and may not be true for bumpy tracks.