No I havent, I've been meaning too, when the rental house house sells and I'm not paying for two mortgages and bills its on the shoppping list.
I don't mean to insult those dont use their bikes anywhere other than tarmac and on sunny days, but to treat the GS like a Chelsea Tractor is to have missed the point of what the bike is about, at the end of the day its only metal and plastic and can be replaced, as long as you have a good set of crash bars for damage limitation riding on green lanes is very rewarding and worth the risk.
No where else can you just cruise along at 10mph to just admire the fantastic view and stop for a chat with people along the way.