"I have been contemplating whether a big American flag on the back of our bicycles would help with one of the hazards of biking my children to work in downtown Seattle: folks in big trucks, who are not used to bicycles. One fellow yelled at my husband and 2 yr old for 4 blocks once as they all rolled slowly along 5th Ave. How did you attach yours?" - Molly
I have only had positive feedback from drivers when flying Old Glory on the back of the bike. Instead of honking in frustration, they honk and wave as they pass with plenty of room and give a thumbs-up. I met a local couple that toured the entire United States by tandem with a small American flag on their rear rack; they testified that it may have saved them from being run off the road on more than one occasion. Bottom line: It can't hurt.
Here's a behind-the-freeloader look at our DIY flag pole holder on an Xtracycle.
Drilled a row of holes to make a slot for the U-clamp.
Zip-tied top of PVC to V-rack
Insert flagpole of smaller diameter and ride.