I ride with the Angry Scotsmen (the Nor Cal club that Arizona Scot referred to). We haven't done a club ride kilted (yet), but we do have members that aren't afraid to do it. Another Nor Cal club that rides kilted occassionaly is the Vampires. They do an annual kilted club ride.

Depending on what bike I ride, my approach to protection would change. On my Duc I have a plastic tank so my kilt would have to be safety pinned front to back between the legs to avoid ballooning. On my bobber I have a steel tank so I would follow my club brother's lead and use a super strong magnet to pin my kilt to my tank.

Since I tend to ride faster on my Duc than I do on my bobber, I would probably opt for street hockey shin guards while on my Duc. I'd deal with the road rash if I dropped my bobber at surface street speeds.

By the way, getting hit by stuff hurts no matter what you're riding. I got hit in the neck by a bird at 60+mph (Think I'm kidding? Ask Tim_C). That sucked, but I didn't wreck my bike either. A little pain is part of the riding experience. Wearing a kilt would not have changed that. How you react to that stuff is the difference between wrecking and riding.