I totally disagree with above comments about limited range of the R2 20m. I am about the same weight as above (85kg) and ride the 20m with a 136 board in 8 knots no problem - in fact I am usually the last guy on the water when the wind drops.
Top end of the 20m is closer to 17 knots, but I think this depends on how hard you are prepared to edge. I have found the kite has a limited de-power but can be controlled in overpowered conditions by edging to push it to the edge of the window.
Also, when most kites have to be worked hard in light conditions, the 20m has good low end and can be parked very early.