Can't help directly but at 5'9" I was initially recommended Small but once I had input 32" inside leg and relatively long arms for my height I then just scraped into the Medium size on their sizing calculator. Shortening the arm length by a centimetre put me back onto Small.
I expect it depends on your relative leg/arm/torso length so make sure you put them in accurately.
At the moment I have a Medium on order but am getting tempted by some of the 2011 model sales starting to appear in the local shops here in Poole who ultimately I would prefer to support, and have the backup of, so I may cancel it.
I don't have any compunction in cancelling a german direct-sales manufacturer order!