The USACG is probably a one-off, they do a lot of hand work there and can build you just about anything you want, for a price of course. That cut doesn't even look like it's be hard to add to an existing body, BTW. Swamp ash is really soft... my favorite wood saw these days is a tungsten carbide blade in a hacksaw, it'll rip through maple. To get that curve, I'd drill some holes and saw up to them, then take out the connecting tissue with a chisel. Three hours, tops, including rasping and sanding to the finishing stage. First, three days agonizing over drawings. :laughing7:
Why go to a gym when you can do manual labor.... :hello2: