I could be complicating things unnecessarily but what the heck,,I installed 3/16" x 1 1/2" ss rings in the deck with less than 1/2 of the ring showing. It was something different and didn't present as much of a bump as a u-bolt. Course that was near the ends, primarily for turning the kayak over on the aft end without worrying about digging the deck in the dirt. For your rudderered stern it could be done but would require some under deck wood/epoxy before the deck goes on. Honestly for the stern if you've got a substantial perimeter line just go for carrying the hull with two hands under the keel.
One of the minor things that bothered me about on deck rudders was how lines/stuff could get caught between the deck and rudder or the tip of the rudder on deck presented a sharp edge to be hit. On a flat aft deck s&g I put a piece of tapered round wood (actually a small winch pedestal made of teak) that was cut in half with a tapered slot for the end of the rudder. When the kayak was on deck you could run your hand down the deck up the pedastal and over the blade without any stops,,same for any lines. I figured it would reduce one significant sharp point during a cowbow rescue.