I appreciate your desire for minimum weight. One thing you might consider is the two-pound, seven-ounce MSR TrekkerTarp ($129; www.msrcorp.com). Using your trekking poles for support, it can be configured much like a tent or as a shelter with a covered front "porch." You can even add a mesh, bug-proof insert ($79), although this will add nearly two pounds. GoLite makes a tarp called the Cave 1 ($119; golite.com), a very spartan system indeed. But, set up properly, it'll keep the rain off and weighs only 14 ounces. Add a 12-ounce bug shelter underneath, also from GoLite, for $69.
The alternative is to get a super-light tent, which would have the advantage of much better wind resistance and, of course, built-in bug netting. But that'll add a pound or two. Sierra Designs' Ultra Light Year CD ($189; www.sierradesigns.com) uses light materials and a trim design to pare the weight down to two pounds, nine ounces. Pack only the fly and a ground cover, and you can trim that load to one pound, 11 ounces. Bibler's single-wall I-Tent (www.biblertents.com) comes in at just over four pounds, but this is probably the most weatherproof four pounds out there. Alas, the price is a burden$539. I also like The North Face's Canyonlands ($179; www.thenorthface.com), a solo tent that weighs just over three pounds.
Whatever your choice, hope you have a great hike!