Hey, I'm about 85kg, sometimes a bit more when there is no wind
I don't know the real windranges 'cause I usually don't measure the wind when rigging up.
If the wind feels low I rig up my 15m and if it's average the 12m will do. 7m only if it's nuking!
I would say the 15m works for me from 13/14 knts - 20/22 knts, the 12m from 15/17 - 26/28 knts
and the 7m from 25/27 - X knts. All depending if I'm riding in flatwater/chop/wave and waveboard-strapless/freestyleboard-straps/wakeboard-boots.
But I'm very curious about the new HiFi 09 and the HiFi Comp! If the 12m turns a bit faster I will definitly go for 7/9/12 range =)