: Since I am starting to worry that the boat will end up weighing a lot, I am
: debating whether to use one 6 oz. layer on the hull and deck plus a
: "sacrificial tape" along the keel, instead of putting two 6 oz.
: layers on the hull. What did you do?

YOu're not a big person are you? doubled 6oz is overkill. I covered the hull and deck with two layers of 4oz, the interior with 4oz everywhere,,thin 1 1/2" strips of 4oz over the under deck joints and interior hull chines from the compartments forwards. The cockpit got another layer of 4oz on the bottom and up the sides about one inch with a triangular patch of 4oz in the aft compatments extending fore/aft from the bulkheads about 6". The exterior keeline got another 2" wide strip of 4oz cloth down the center. So basically there's 8oz over all joints and exterior with the cockpit with 8oz on the interior. IMHO this is overbuilding for a 16' kayak for a 150#person,,but I wated a tough boat. I think you could do your entire kayak in 6oz on the exterior with 6oz in the cockpit and up the chines an inch with at least 6oz on both sides of a panel joint to hold things together using strips of 6oz over the interior chine joints and 4oz in the compartments. I just like glassing everything so that's why the 4oz everywhere.

For your weight putting down two layers of 6oz on the hull is overkill,,honestly you could do a lot of combinations but 6oz is pretty much the doall tough exterior layer. It's worth putting at least 4oz on the cockpit floor.
I wouldn't bother with 3" tape down the exterior keeline,,it's such a pain fairing in and really doesn't address the likely bumps and scrapes midway out from the keeline next to the chines under your seat.