You want flush with sink...NO overlap. If you have overlap its just a place for 'gunk' to accumulate. Tell them you do not want the granite to be over the sink.

I think the reason they suggested 'over' is because it's easier for them. They don't have to be as exact as they do if it's flush. Just my opinion but I wouldn't have it 'over'. HTH

old, I'm a computer idiot so don't know how to post a thread here, but you can go to the bottom of the page and where it says "search" type in "undermount sink." Then do the search. The first post that comes up is a very good one on this exact issue. I myself finally decided to go with a slight positive reveal on my Shaw sink. One thing was the gunk factor that is mentioned, the other was the idea that you could "wop" a pot on the bottom edge of the granite as you were pulling the pot out of the sink with a negative reveal. My other thought was that I might buy a stainless sink grid for my Shaw sink and I was not sure I could fit it in if I had a negative reveal on the sink. Hope you get what all I'm saying here. But, bottom line to any and all of this......it is your final choice to make. Good luck.