We have been blessed with excellent winter wind and snow this winter so far (more wind to come tommorrow).
I went out kitesnowboarding today with my foil/sled Concept Air 6.0 EX's (depowered as a sled) in wind around 17 to 27 knots (peak gust 30.8 knots). I was a bit overpowered but did just fine. This is the wind I normally use my Naish 5.5.
I also use my foil/sled Concept Air 6.0 EX's as a flat foil in 10-11 to 18 knots (the wind I normally I use my Naish 11.5 for from 9 - 18 knots).
So my sled/foil Concept Air 6.0 EX's is almost equal the Naish 5.5 and 11.5.
P.S. I start using same kite sizes for kitesnowboarding as for kitesurfing (as long as you have some snow to edge decently it's the same); because it's easier and higher to jump in power-up condition.
P.P.S., And this is in cold air around -20C. I am not sure what the wind meter that the yatch club nearby used but it seems to measure both winter wind and summer wind similarly (same power as I feel from my kite)
P.P.P.S, I am in the process of converting my XXXL to a foil/sled.