Thank you all for your input! I drew it on paper and the lights look too close together using the 1/3 rule (28" from edge), and they look too far apart centering them on the sides of the sink (13.5" from edge). So, I've decided to split the difference and center them 21" from the ends. This gives 24" between the pendants in the center of the island, and 12" from the edge of the island to the pendant. Even with hubby being 6'5", I don't think he'll hit his head. I drew it out (side view and top view below). Please let me know if there are any fatal flaws in this plan! p.s., our ceilings are 9', so I can easily have the bottom of the pendants 36" from the top of the island - thanks for the tip Jan!

We are using 3 of the 10" Pottery Barn City Glass pendants over our 9' island. I was also worried about having enough task lighting, so we added a can light over the island sink. Just wanted to add that many use lanterns over the island for an airy look and plenty of light.

Wow....Ok.....I read a confusing article on how to calculate this just now.....there are a bunch of rules and it can depend on the size of the room and the height of the ceiling. But the rule that made the most sense to me is that you want the 6 inches of space around the perimeter of the island to be free of lighting so that someone sitting down or leaning over the island wouldn't bump their head on a fixture. So taking into account the width of your island which is the smallest measurement, is 40". Then subtract 12" from that and that leaves you a maximum width of 28". That's a BIG pendant IMO. Also if you are using two fixtures, according to the "rules" (I would call them guidelines and you should feel free to break the "rules", you should have the same amount of space between the pendants as they are wide. So, if you find a 20" pendant then you should have 20" between the two as well. In that case considering your length, your pendants would hang covering 60 inches of island from the middle. That means you'd have 24" free at either end of the island. I see that one you are showing on the Kichler site (the Everly is the one I think) and I see one that is 19.75" and one that is 15.5". I've read others on here saying they found balloons approximately the size of the light fixture and hung them from the ceiling to approximate the size and look. It might be worth a try. Or worst case scenario, order one of each size and see which one appeals the most (assuming they have a good return policy). I do like the fixture you've chosen, it looks very nice.

@lucky998877 the picture makes it look a little weird, but the edge of it falls about 6.5-7" from the edge of the counter. The new ones would be about 5.5-6" smaller in diameter so they'd be a little closer in towards the middle. I think the "hole" (not sure the right term) where it attaches to the ceiling is about 15" from the edge of the counter.