Floyd,
I do share your concerns: a 3.0 sail is way too big a sail for such wind force. However, water surface is not a problem anymore because it's not open ocean; it's a lake and gale force winds tend to flatten the swell/waves quite a bit. Some pictures with 10 Bft (recorded 90-100 km/h wind speed) on lake Geneva last November :
http://www.music-roman.com/Photos/Lac_1g.JPG
http://www.music-roman.com/Photos/Lac_6.JPG
Cheers !
JM