Well... 12 seat means about 24' or more. Unless it seats people on both sides.
Do they want a bar rail?
I built one last year with a fairly simple bullnose out of White Oak. Big shaper bit for that. The contractor who did the rest of the work there had built the base & sub-top, so this basically sat on top of that, screwed from underneath. You can't see it here, but there's also the back bar shelf- that was basically just another piece of Oak fastened to the bottom of the bar- the bartender will keep various items on there, or set your tab there.
Are you building the base, too?
What is the rest of the restaurant like?
So many questions...
