If someone is going to sit on it, or stand on it, you will need support. Steel tube frame, properly integrated and attached to the cabinets. . Plywood flexes way too much. I’ve seen the cracks where someone relied on that.

I would not use that bracket without significantly reinforcing the cabinet back. And routing it out to sit flush. I don’t really like the look of that much period. I’d just TIG well some of the aluminum tubing off the shelf at Lowes in an H pattern and install that to a pony wall if there is one. and use that. You’d probably contact a local metal fabricator to do something similar.

If there isn’t a pony wall to attach too, you’re gonna have to get more complicated.

The overhang is on the peninsula which is connected to a wall wall - L shaped - long part ot the L on the wall - little part of the L is the peninsula.

I don't know how thick the corian is, I will have to ask. how thick it will be.

"If 3/4" you do not need support."

I bought the last of my distributor's 3/4" Corian in 1998. There is no more.

Kristel:

If you're using 1/2" Corian with a 1" build up, screw some 1" aluminum square tube spaced every 24" as underlayment screwed to your cabinets that spans your cabinets and cantilevers 9" or so. It will be more than enough.

By way of a 2019 update, some users are reporting that Glacier White Corian is now available in the 19 mm (3/4") thickness. According to Corian.com, all colors in the standard color palette are available in 12 mm (1/2") sheets, and some color options may be available in 19 mm (3/4") sheets or 6 mm (1/4") sheets. I'd be curious to know how much thickness is usually removed every time the surface is refinished in a job with no terribly deep scratches to remediate.

The surface is only removed to the depth of the scratches. You'll be dead before your refinisher makes the top too thin.