Here is just a thought (and I know nothing about DIY), Awesome idea Frawg & Rock, but to just modify your idea a smidge.

What about using DynaGlide continuous loops instead of the paracord loop, with Cuben-loops attaching it to the tarp?

Or, on second thought, you should have a 'safe' place for the connection to fail, and dynaglide/Cuben won't fail nicely.