There are some other recent threads about island configurations that could help with your question. Here is one:

Here is a link that might be useful: http://ths.gardenweb.com/forums/load/kitchbath/msg062357224984.html

Here's another one where I showed how we supported our overhang and the cabinet arrangement for our island. We have a 15" overhang plus a row of 12" cabinets behind the front row of 24" cabinets so our island is 4' 4.5" wide (including the 1 1/2" overhang on the front).

You could also use 30" deep cabinets as the base plus your 15" overhang. Methods of support are usually either metal (like in ours or metal bars attached to the top of cabinets without plywood under top), corbels or legs.

Here is a link that might be useful: http://ths.gardenweb.com/forums/load/kitchbath/msg062153235455.html

LOL!!! I forgot about my own thread!! Duh!!

Ok, question though.... what do you use the 12" cabinets for? Are they hard to get to.

As I mentioned in the other thread, the two end cabinets in the 12" row have doors on the sides of the islands. They are the same to reach as any other cabinet. One is in our baking area (the mixer and bread machine are on the wall counter opposite it. We store baking sheets and cooling racks in the bottom of that and have a pull out shelf with other baking pans above that. The other one is near our prep sink and has pull out shelves for cutting boards, food processor accessories (DH built a divider customized to hold them) and some other stuff.

Between them are 12" deep shelves with doors opening under the overhang. They aren't bad to get into. It is easier than reaching in to stuff in the back half of 24" deep fixed shelf cabinets because you don't have to reach past anything. One holds stuff that we don't use that often like the waffle maker, candle lanterns for outside or power failure, etc. The other contains some pantry items - things that we need more frequently because it is closer than the pantry. As that suggests, we find it easy to use. We have to reach under the overhang, but it is shallow so it's easy to see everything. Of course if someone is sitting or standing there, we have to ask them to move to get into it.

Our old island just had dead space there - 36" deep of built in place cabinets but no doors to get into the back 12". I definitely prefer this.

Cloud swift... Thanks so much for your answers! Between what you have said and the others on "my" other thread (which I forgot about), I think I have a better understanding.

So back to my trusty graph paper!!