I'm in the 190-200 lb range, size 10.5 boots, cobra 161. I could get away with a 158, but powder days would suffer. It's plenty responsive edge to edge, holds a carve line very well, will go as fast as you care to let it. Overhang is about as much as I think it needs to be.
At 275, and with size 11.5 feet, your gonna need to stay on a wide. I haven't ridden a custom, but I can tell you that the cobra has much faster edge to edge than other boards of the same size that I've ridden. I realize that's not much of a reference, but my point is that board shape, rocker design, etc make a big difference in feel.
My opinion is that for what you describe and with your size, you need a 166 cobra x, assuming you want to go never summer.