I finally figured out how to attache the gudgeons and traveler without a helper. I put the boat upside down on the top rack of the trailer. I could then stand up and get under the back deck. I used a vice grip to hold the captive nut while I tightened it with a screwdriver. Last part was the rudder lock. I made that out of a small chainplate.
And lastly, a centerboard for Griff. This board has a big 11 1/4 inch chord. Big boards for a vintage boat.