If you do a search on the internet, you'll find that the standard overhang allowance for a countertop (think breakfast bar) is 12" unsupported.
I asked DuPont which countertop surface will allow for the greatest overhang. Surprisingly, I received a detailed answer from a human, rather than an automated reply.
Here it is:- Corian 1/2" material can have an overhang up to 6" unsupported.
- Zodiaq 3/4" can have an overhang up to 12" unsupported.
- Zodiaq 1 1/8" can have an overhang up to 15" unsupported.
- Granite certified by DuPont (sold at Lowe's), can have an overhang up to 10" to 15" unsupported.