For years I have been thinking of this idea while setting up the tarps, which we call the Casbah. The tarps we always use had limited grommets and were bulky, not to mention all the bungees we would bring.
This year I am putting my idea to the test. I bought 4 lightweight tarps at REI, 2-8'x9.5' @ 2-9.5x12', added 108 grommets total to the 4, and am going to use all rope and the figure 9 things. The idea with all the grommets is that no matter how it is configured the grommets line up on the different tarps and the sides can be sewn together.
The pictures show the "ideal" set up without beingtied down very well of course and the figure 9 things were tested on the 4th of July when it rained all day and got fairly windy(didn't slip).
So I present the U.C.K.?

Very interesting idea. How does it hold up in a 60 knot blow?

I'll find out. Shouldn't be any worse than what we were using.

To further explain: I've only been on a trip with less than 6 people once and housing them for hanging out in rain is always an issue. This year it's 8 people and a dog. It weighs 7 lbs. and is much less bulky than our current system. The gear bag weight is never an issue, it's always the food pack, which we've gotten down to a reasonable size lately.

What was your total investment in time and dollars?

you should be good for just about anything with that!!..
one suggestion--mark the corners of each tarp in some way.i made a large Baker tent style shelter nicknamed the "dance hall" by my buddys because it's so large.it's made from Sil-nylon and when i pull it out of the stuff bag it's a mess to pull and turn to find the door with all that material..i have the door corners marked with blue and yellow patches and that really helps.same with yours.pulling it from the bag in the rain and being able to say "here's the corner,tie it off" would help get it up faster.

The Tarp Mahal! Nicely done.

The blue tarp is the roof.