I built a regallo wing hang glider in the 1970s based on an article in, I believe, Popular Mechanics. It was built out of aluminum pipe and clear plastic sheet. It was 18 feet long and had a 27 foot wingspan, and was really a big kite. We flew it down hills in Louisiana. At the time we built it, the motto of the hang glider club in California mentioned in the magazine article was "Never fly higher than you are willing to fall" - a rule we never violated! Fun, but in hindsight, risky. Be careful.