As promised here are pictures of the supports installed. We couldn't do the steel sheet because on the backside of the 12" cabinets, which face the overhang, is the sink. Stacy at Amastin knew what type of granite we had and the cabinet layout and recommended installing two supports at approximately 31" apart where cabinet boxes joined together and we had extra support below. The supports are 24" long - 12" on cabinets, 12" overhang. We realize that the supports are farther apart than the typically recommend 16-20", max of 24", but it was by far better than not having any supports at all and we are happy with the solution. We also were very impressed with Amastin's customer service and would gladly use him again in the future. Here are the pictures before and after install. If anyone would like more information just let me know.

I know fabricators sometimes use metal strips to brace overhangs. They are basically invisible and very strong. I think sometimes (maybe always?) they are inset into the granite. I would want to do that and then use some lighter, more graceful corbels on the corners. I believe the corbels would serve an aesthetic purpose more than a functional one. I agree that almost 4'' thick top is way too much.

I worry when my 200 lb teenage son puts weight on my 12" overhang ... yours just seems like an accident waiting to happen. I would never think of putting weight on a cantilevered surface like this, but most people don't even give it a thought and some would even hop up and attempt to sit there!

Yes, you will still need support. Check the "Stone Information and Advice" thread for more information, but to summarize.... countertop support: Supporting the width of the countertop: You need a corbel or support every 30 linear inches of unsupported overhang Supporting the depth of the countertop: General: You need to support at least 2/3 the entire depth of the stone, so assuming you have 24" deep cabinets on one side of the island and your seating overhang is on the other side, you need the following: If your granite is 2 cm thick, then there can be no more then 6" of of unsupported span with a 5/8" subtop If your granite is 3 cm thick, then there can be no more then 10" of unsupported span - no subtop required If you need support, then to determine your corbel dimensions: . Thickness of Stone - Dimension of Unsupported Span = Corbel Dimension . i.e., an 18" total overhang in 2 cm would require a 12" corbel; the same overhang in 3 cm would require an 8" corbel If you are using a pony wall or cabinets with a depth of less than 2 times the depth of the overhang, then you need to provide support to equal at least 2/3 of the total depth of the countertop.