No, I haven't...I have considered it, and, in fact, just last week I dug up an old chart on tire pressure / tire size / weight that shows recommended tire pressures based on total weight (rider and bike) based on tire width. My conclusion after studying the chart is that I could go down to 100 psi maybe but any lower I'd be risking pinch flats. That's why I'm considering larger tires.

I consulted an old Frank Berto book, Bicycle Quarterly (which had an extensive article on this), and, of course Sheldon Brown...

http://www.sheldonbrown.com/tires.html

Maybe I'm being too cautious, though..