Man, I'm glad you walked away from that. Bummer about the GS.
We have a mountain (foothill) pass here with bad gusty winds. The danger comes when passing 18-wheelers who are slowly climbing hills. I almost rear ended one when I was blown into his lane just before overtaking him doing 3 times his speed. I nearly lifted the rear tire getting on the brakes.
That was on a Ninja. My Honda XL600R didn't do any better loaded with gear, but my Aprilia Dorsoduro is noticeably better, especially with saddlebags and top box mounted. I suppose the 410 lb supermoto has the advantage over the 320 lb Honda dual sport, but can't figure out why the bags help. The Ninja was just a sail.
It must have been really bad to blow the GS around.