I'm a little OCD about things being centered. If it will drive you crazy fix it now. If it's not going to bother you just forget it & go forward. If it were me I would fix the sink & move on.

I would move it, too. Predrill the holes before screwing into the back rails to prevent further splitting?

It's not a mistake yet if you can fix it. I would not leave something that I know is going to be off. It's one thing if it happened not knowing but knowing and not getting it done right would not sit well with me. I'd rather not regret something if it could be avoided. I'd get it done the right way now when you can so as not to regret it later when it can't be fixed and having to live with it. A couple of hundred dollars now compared to looking at it for years as a regret/mistake is a small price to pay.

I would fix it and move on, but I am seriously concerned that you're being taken in $200 increments. You need to get something from them that when this is fixed there are no further issues so that you can move on rather than fix this problem and have them come back with yet one more. That being said I can't imagine putting a cast-iron sink into a cabinet where the material split and not being nervous. The last time I looked at one of Kohler's manuals there were several ways to hold that sink in the cabinet. Rather than be a little nervous about it, you should make sure that the sink is supported properly. It will be much much more costly for you if after you have the granite countertop installed the sink separates from the countertop and begins to fall downwards.

The cabinet installer who left an out-of-level cabinet needs to pay the $200.00 back charge for the re-template. It's not the countertop company's fault the cabinets and sink were installed improperly. They are covering their butts so when your brother-in-law comes over and spots the sink out of center and out of square, they can say "We told you so." I would do the exact thing they are doing.

Get the sink centered, square, and mounted securely. Pay for a third templating. You'll never have an opportunity to fix this for $200.00 again, I promise.

I'd leave it. Imperfections that minor should be embraced IMHO.

On the other hand, I missed the sink center on my own 60/40 by an inch and never saw it again.

I'd leave it and move on. I don't think the 1/8' will be noticed, and the centering wouldn't bother me. When we moved, I realized our island wasn't centered in the u-shaped kitchen. I hadn't noticed in 8 years.

I would leave it. I am one of those persons that everything needs to be symmetrical. But on a horizontal surface I wouldn't ever notice it. Less than 1 inch no one will notice but you. My sink may end up not being in the center of my window due to limited cabinet sizing. As it will only be off by an inch or so I am just going to make sure that I can mount my faucet in the center of my window without it looking odd.

My sink cabinet is not perfectly centered under my window - the granite installers pointed it out to me when they were there for templating. It's off about a half inch. I'm borderline OCD about matching and symmetry....and had not noticed it. It's been 4 years now and the only time I ever notice it is if I'm standing dead center and visually line it up with the window. 99.99% of the time people don't do that. :) Think about how many kitchens you've been in during your lifetime - was every one of them perfect, or are chances good they too all had tiny little imperfections you never noticed?

You won't notice it once everything is in. Just move on. :)

Oh, fix it!
7/8" is almost an inch. I know it would drive me INSANE, simply because I would know. Yes, OCD. But I can SEE a 16th of an inch out of whack.

I'm working towards soapstone counters and sink. One of the biggest reasons I'm excited, is that when my ex-GC DH put the current sink in, it's not centered in the cabinet. It' makes me crazy.

I'd also go back to the cabinet installers. That's a lot of dollars for that to keep happening.