I visited Gig Harbor Boat Works this afternoon. Falk suggested a hardware change where the bobstay connects to the stem that will eliminate a potential water penetration point in my design. He also showed me an option for a stainless steel keel strip, and how to best use it on my boat. Then he gave me a tutorial comparing oarlock types—circular, oval, and "D."
I learned that compared to the circular oarlocks, the oval ones (oriented vertically) do a better job of keeping the oar seated properly while allowing good movement up and down. The advantage that the "D" oarlocks (combined with a flat face on each oar) provide over the other two styles is knowing precisely how your blade is oriented. A trade-off, however, is greater potential costs.
GHBW is sponsoring a sliding seat for rowing Kingsfold. Check out their sliding seat hardware here.
In defense of round oarlocks, Nate Rooks of Team Bunny Whaler (Full Race in 2016, Stage 1 in 2017) told me,
"Tim Penhallow used round oarlocks (just like you have) and oars for the whole way, usually rowing ~15 hours a day."