VFR C170 pilot descended through a cloud layer without clearance after strong head winds increase fuel consumption.

Narrative

My wife and I were returning to Indiana from Florida; in our Cessna 170. Departed Florida; and refueled in GA. Diverted east-northeast toward Roanoke; VA; due to slow moving storm system across direct route to my destination. About 40 miles west of Roanoke; I was able to turn NNW; toward southeastern Ohio. We had been getting beat up pretty good with turbulence; and I climbed above a scattered layer into smooth air; climbing to 6500 MSL. The layer gradually increased in altitude; and I climbed to 8500 MSL to maintain VFR cloud clearances. Everything was still fine at this point; but I was about to make a very poor decision. The cloud layer gradually increased to a continuous layer. The cloud layer was expected; but I expected to be well past the cloud layer before having to descend in mid-Ohio for fuel; and I stayed above the layer rather than backtracking and descending below the layer. This was a poor decision. The wind gradually increased to about 40 KTS headwind. It gradually became clear to me that I did not have adequate fuel to get past the layer. The cloud layer did indeed turn out to disappear approximately where I expected it to; but I could not get there with the fuel on board. I was way too far into the corner I created; by the time I admitted to it to myself. At this point; I did not believe backtracking was a reasonable option. The storm system; which I had done; an end-run around was slowly moving toward the route I had flown; the terrain behind me was higher; and the ceiling under the cloud layer was minimal. AWOS stations ahead of me were reporting ceiling of greater than 6000 FT; some of them reporting broken layer. I was still hoping that I would find a break in the cloud layer; and be able to stay legal VFR. I finally realized that I had to choose between two poor options: 1. High probability of running out of fuel in flight if I continued trying to fly past the cloud layer. 2. Descend through the cloud layer; even though I am only VFR rated. I chose to descend through the cloud layer. I set up a heading toward a nearby airport reporting high ceiling; stabilized descent; and descended on instruments. The layer was not very thick; but I did not maintain VFR cloud clearance requirements. Center would have known where and at what altitude I was; from my transponder. Hopefully there was no other airplane cruising in that layer. My altimeter and transponder do have a recent IFR certification. After breaking out; I landed; and refueled. Remaining fuel was minimal. I then continued on to my destination in Indiana. Within about 30 miles; the ceiling was unlimited. This is only about the third time that I have ever proceeded on top of an undercast. I did not plan to do it. I did not have adequate and recent enough weather information to commit to that course of action; particularly with the fuel on board. I have been kicking around the idea of getting my instrument and commercial ratings; thinking that it would be an interesting thing to learn; even though I have no desire to actually do instrument flying on a regular basis. This event has pushed me further in that direction. The jam I got myself into was my responsibility; caused by my poor decisions and not leaving a legal and safe way out. Fortunately; the minimal instrument time that I get every two years during biennial flight review allowed me to keep the airplane under control.