How to roast a fish in salt

How long to roast it? James Beard suggests the Canadian Fisheries method, 10 minutes per inch (2.5 cm) of thickness, measured at the fish's thickest point; Luciano instead says some people cook a minute per centimeter of length (2 1/2 minutes per inch), and others 20 minutes per kilo (about 8 minutes/pound), but notes that different fish cook at different rates, so a few minutes before the projected time he scrapes away enough salt from the belly of the fish to reach one of the belly fins and pulls gently at it; if it comes away the fish is done. If it doesn't come away her replaces the salt and tries again after 3-4 minutes.