Just jumped back on after a few months & saw this one. I wish I could offer more info on this Jay roughs topic, as we all wanted to know the same thing back in the turn of the millenium too. But there never seemed to be a clear answer. I hung out at Jay's place in Chicago in '99, and saw all the stacks of boxes. He was so generous with his time, and showed us stacks of roughs and unpublished stuff, chatting for hours & going to dinner with us. But from what I remember of it all, the accounts on this thread sound about right. I remember him distinctly saying that Art did the early stuff, and he was brought on later. Since much of the 2nd series came from the Wacky Ads, I always assumed Jay didn't start until the 3rd. But since then so many sheets and evidence have come up with titles like Taster's Choke & Bald having earlier origins than originally thought, and untitled's like Buggies surfacing. Jay seemed to know a lot about the Wacky Ads, too. So, it certainly sounded like he was around & part of the action early anyway. I remember there even being a spooky "Wacky Ads came before the Die Cuts" period for a while, which may have gotten debunked. (iPad actually came before iPhone regardless of release times, so anything's possible).
Not sure about the 100 or less #. I always had the impression that Jay pitched more stuff than 20%, too. But I also remember mention of another rough artist (not Art, Len, etc... someone else). Bunk?... or was he much later?... Might have been the same person who did the non-Saunders final pieces (which also seem to be up for debate as no one would argue that 6Urp wasn't Saunders, but the simple, flat or line-drawing titles, like Mold-Rush, PlayDumb, Blisterine, etc. don't look like Saunders, but still could have been). I do also remember Jay saying that everything was moving so fast when they were popular that it wasn't really logged who did what at the time. Otherwise there would be some kind of list.
Anyway... not that my often-absent-from-these-discussions opinion matters, but given the detailed lists I used to keep, and sleuthing I used to do, I definitely would have kept a total if one had been available from Jay back then. I could probably tell you who owned which piece of known final art back in 2000 (which would be severely inaccurate now, for certain). Sadly, I only ever owned 3 or 4 Jay roughs & didn't hang on to them.