Thanks all for the thoughts. I have been in huge blows while away from my tent....daytripping as it were. During one especially memorable event I remember I could lean forward into the wind and not fall. My chief concern was wether my tent along with my sleeping bag would still be there when I got back. Fortunately not only did I stake the tent out but I had used the additional guy line attachment points as well (something I don't ordinarily do).

There are many unknowns when one has to depend on rocks to tie off to. If they are especially smooth and rounded or oval (as I suspect I will encounter in Georgian Bay) I would not trust the lines to stay secure during a big blow. Perhaps I am not acquainted with the right methodology.