In addition to attending a game inside Chez Amazin' last night, I had a chance to walk out to the parking lot to see where Shea Stadium's bases and pitcher's mound were located.
Go to the 3B side of the Promenade, where the ticket windows are. Go to the outfield side (left if you're looking at the ballpark) to where you see one of the staircases and gates (if you've hit the VIP entrance, you've gone too far). get even with the staircase that's on the home plate side, just next to the Citi Field map and ticket windows. Walk straight away from the ballpark to the parking lot. About 400 feet away is second base, and the rest are in line from there.
When I found the markings, two things seemed wrong to me. It's probably just my perception and inability to judge distance. The bases seemed less than 90 feet apart from each other. But I'm looking in an open parking lot and not in the context of a baseball field/stadium (which I haven't been on an MLB size diamond on the diamond itself in a long time). They diamond as a whole seemed too close to Citi Field. Again, same perception or lack thereof. I know that the batter's eye from Shea almost bumped up against Citi Field, on what is now the big sidewalk outside the ticket windows. I need to find aerial shots of them together and Citi by itself to judge better. The one thing I wouldn't want to see, but would help greatly with the perception would be a chalk outline of Shea, marking the playing surface features and the exterior wall of the stadium. I could have walked 410 feet from home plate through second base towards the new ballpark (where it's a perfect 90 degree angle with the outside wall), but I stopped counting at 14 paces and got on line to go inside. I did exit from the stairwell that lets out right in that line, probably 450 feed from Shea's home plate.
I have pictures of it on my camera, but nothing that you haven't already seen elsewhere.