These two photos show the layout of the plumbing: https://www.flickr.com/photos/90278919@N00/16272219299/ https://www.flickr.com/photos/90278919@N00/16458466225/in/photostream/
The center of the left bowl's drain was about 3/8" too close to the entrance to the p-trap. https://www.flickr.com/photos/90278919@N00/15836084224/in/photostream/
So I attempted to shorten the horizontal pipe from the output of the 90-degree elbow to the y-connection at the rear wall. I ended up with this:
Note the 1/16-1/8" inch gap. The item with the bar code is a repair coupling. After priming and doping it, you slide it over the junction of the two pipes you are joining. Obviously, at the left end there is nothing for it to grab on to.
The repair coupling is 1.5" long. If it were, say, 1.0" I could probably cut back the pipe it's on enough to allow gluing an short extension - maybe with 1/2" visible onto the output of the 90-degree elbow. Then the coupling could slide over 1/2" of each pipe.
I'm horrible at cutting 1.5" PVC pipe with a hacksaw and getting square cuts, so what I just suggested would be a challenge for me.
Can anyone think of a different approach?