Tile Counters

[tpugh]

I am installing granite tile as my counter top.  I have several questions: 

I am considering what size tile to use.  I am leaning toward a 24" to have the least seams, How much overhang should I leave from the cabinet face?  If the 24" are too small, then I will use 18" any advice? 

I want the least obvious seams, What is the least gap between tile I can leave? 
Will epoxy grout, flowing or knife grade give the best look and feel without having to polish? 

I don't really want to buy special tools to polish the edge.  How good of a finish can I achieve with the silicon carbide sandpaper and a DA sander?  I have a high-speed 4" angle grinder too. 

What layers of sub-straight do I need?  Ex: 1/2 plywood and 1/4 backer (glued and screwed)

I have never worked with granite tile, any other tips would be greatly appreciated

Thanks
Todd

[Mark D.]

Todd,
Lots of stuff for you here. The overhang is a preference unless you are going more than a quarter of the tile.

You can go down to 1/8" or even 1/16" for the grout joint.
I would use epoxy grout in the kitchen. It will dry with some polish. Make sure you use a sealer on the stone before you grout. It will act as a grout release and prevent the stone from getting stained by the grout. Use this:
http://www.defusco.com/Glues:-Epoxy,-Polyester,-etc.-Hydrex-Sealer/c82_502/p2095/TENAX-IMPREGNATOR-AND-SEALER---1-LITER/product_info.html

Silicon carbide will work but will take forever on granite. It is much better on softer materials like marble or travertine. If you own a variable speed grinder here is a low cost diamond polishing pad set that will give you professional results dry polishing.:
http://www.defusco.com/Diamond-Products-Diamond-Polishing-Pads-&-Backers-Diamante-Italia-422-dry-resin-pol/c25_30_652/p2009/422-RESIN-DRY-POLISHING-PAD---FULL-SET/product_info.html

The substrate you describe is good for stone tiles. Use a latex thinset for adhesion.

Glad to be of service,
Mark