To the person who mentioned Bill Rodgers, I had the same impression. I didn't run behind him, but met him a few years ago. My first thought on seeing this childhood here of mine was he is built like a little boy, still, and then I thought, despite my dreams, I had little chance of ever being a world class marathon runner like him.
The critical question with all this talk of size/weight is does one's cardiovascular abilities, for lack of a better term, increase with size. That is, is a larger runner able to compensate for more mass with with a bigger engine, thus making mass an irrelevant factor. I suspect, no. So, Solinksy's achievement is quite amazing. He's got the frame of an steel frame Schwinn bike and, more typically, the word's best are hopping around on carbon fiber racing frames.
His build is much more in line with some world class steeple chasers of the past of North America and Europe.