Some ultra-light backpackers have sub 20 lbs packs including water for 3 or 4 day trips! I would think you could do this with a seatpost rack. I ride everyday to work with an Old race bike (le mans centurian) using a seat post rack and one pannier. because of the angle of the seat post tube this rack holds the pannier up and away from my heels so that is not a problem as I see it (a more traditional rack would creat problems because of the short chain stays). Using a handle bar bag, or strapping a sleeping bag/ or tent to the handlebars would make it possible I think. My main concern would be that race bikes seem to be designed to not handle excessive weight and so the total added weight would be my primary concern. I think if the seatpost rack is mounted right at the top of the seatpost tube, you wouldn't have problems, even if you did you could just get a bit beefier seatpost I would think. This idea has piqued my curiosity. One of these friday nights I am going to have to try this I think.

btw for ideas on going light checkout www.backpacking.net, there are some good ideas for homemade gear as well.