Sorry man, I really tried to get you a good answer.
The best I can do is point you to this guys blog:
His indiana jones style rope bridge that he built is in the photos there, and it looks really cool. Perhaps if you contact him to find out how he built it, he'll give you some instructions or a pointer?
Good luck with the project, it sounds fun!
I thought about it for a few days and came up with an idea that seems to work. I'll have to post the plans and pics when I get the chance.How bad is it that I can not stand my fiancee's 10 year old?