After watching this thread for several days I decided to make one of a similar design last night. I made mine about 22" wide and I guess I could have made it a few inches larger. I wanted one that can easily be pushed back if I need to paddle or use my paddle as an emergency rudder in case the rudder completely fails ... which has happened to me once.
It takes only a few minutes to attach the bungees but I could if need be set it up or take it down on the water with very little effort. It's not something that you should put a heavy object or person on but in an emergency, you could lay a person on it and it would probably be ok. My new thing is to remove the pedals when sailing so now I have somewhere to stow them.
For more pictures http://www.asthmastory.com/ai.php