Got it! (actually, I got it a few days after I posted my question and just threw it in our travel drawer - so when I saw your post just now, I ran out to the garage and tried it.)
The 2006 Peg Perego P3 fit just fine - but I had to remove the snack tray. There is room in the top to slide it in after you get the stroller in, but it took up too much space with the wheels etc when sliding it all in the bag together.
Any bigger of a wheel base when folded (than the P3) or any taller and it probably won't fit. I forgot I had the handles extended when I put it in and it would cover them - but as soon as I realized that and put them back in the standard position, the bag closed just fine and dandy.
I admit, I did pay for shipping. For the 3 or 4 dollars it cost, it was worth it to me to not have to drive anywhere (at $3+ a gallon) and to not have to take DS into a store - especially into the skanky Wal-Mart. I did a web search - put the product in 4 or 5 shopping carts and compared the total cost including shipping - choose who was the cheapest. (Don't remember who I ordered it from, but shipping might vary based on where you live anyway)
HTH!