Re: make a corian counter cutout smaller to fit new sink
I would start with the larger sink idea, if that doesn't work out, then I would contact a corian installer and have them make up a donut to overlay the hole and make it smaller, then set a new top set sink into the donut. It will raise the sink slightly, and give it a wider rim, but it will save replacement if the existing counter is still in good enough shape.
I've used this method with other applications to great success, good luck and report back on your progress.
I suffer from CDO ... Its like OCD, but in alphabetical order, LIKE IT SHOULD BE!!!