Tried it in approx 18 knots with a surfboard, getting out and back but losing ground every time. Pretty sure will stay upwind in a SOLID 20 Knots (Cabrinha ICON 130, 30 Mt lines). Only been out at Scarbs, but I'm sure i would be going up wind on flat water, minus current (woodies, pinneroo). Sweet little kite. I've never flown a more stable kite (in 6 years), ideal for any level on 2 or4 lines, mine on 4.
5 metres.....Brings new meaning to the phrase
" 1 pump ". 
UPDATE: Holding it down yesterday for 3 hours solid, 20 to 35 Knots. Kite fully sheated in, fully powered.....Will wait for some 40+ day to test the depower
..Tried some loops (30 knots) still get some whip..
UPDATE: Mon 19/06, took her out at Scarbs again in some squalls. Spot on for kiting 30 knots plus, super stable in gusts although depower gets limited towards the 40knot mark Held onto it in one squall..literally hangin on....notice some folding, deformation in the centre of the conopy, but only breifly when the squall first approached.( no damage noted on kite following sesh,) Checked the BOM graphs when i got home...seems the kite tops out at 43 knots ...YES 43 KNOTS, THATS 80 KMH....JEEEES.(largest gust registered) Pretty happy with such a large range.....80 KMH no BS. SEE:http://www.bom.gov.au/climate/dwo/200606/html/IDCJDW6121.200606.shtml
www.bom.gov.au/climate/dwo/IDCJDW6121.latest.shtml
My high wind kite is a 9m Grunt 2004. It's also the kite I learnt on so it's been smashed around to the extreme without any adverse effect.
Sweet kite, super stable, responsive, flys upwind radically, tough construction and of course, as the name implies, heaps of grunt...
Bo
My wife took the 5 Grunt out the other day in around 20knots. her only complaint was the kite was real twitchy and fast. She did well and can finally ride in big winds.
