After a lot of consulting with the folks at Race-Lite and with substantial help from Matt at JEM watercraft, we have finally come up with a good solution to the problem of attaching rudders to canoes and kayaks. Use two of these gudgeons for the rudder and two for the boat and them connect them with a 1/4" bolt for each pair or a rod right through all four. The tangs are 1/2" x 0.049" stainless steel and can be bent to adjust to about any rudder or transom.

Here is a set. It includes two of the gudgeons, a 1/4-20 Stainless bolt, two SS washers, and a Stainless Nylok nut. The picture below shows the set disassembled. You will need at least two sets for a complete rudder installation.