Supporting slab overhang

Hi All,

I have a kitchen/bar Counter (http://GialloFiorito.com) top that is about 9' long. I am considering changing from the current two level configuration to a single level Counter (http://GialloFiorito.com) . The current configuration is a 24" x 9' kitchen Counter (http://GialloFiorito.com) with a 2' x 2' section appended, making it an L. There is a 15" deep bar top that overhangs the finished pony wall side about 8".

If I go to a single height top with total depth of about 42" (possibly with a curved edge on the bar side), it looks like the overhang from the pony wall could be around 13". With this overhang, what kind of support for the 5/8" plywood would be required? What is the max recommended overhang before additional support would be required?

Could I use (2) 5/8" or 3/4" sheets of plywood for less deflection, and (http://maplered.com) add a lower edge treatment or go to a taller edge to hide the extra height of the plywood?

Here's a support idea from the Stoneworks site (see the fabricated steel subframe below on the right ): http://homepage.mac.com/Stone (http://g603.net) works/PhotoAlbum40.html

Does anyone apply a waterproof coating to the plywood?

Thanks,

Lee