Rob: According to an old post by Matt B., you may need to move the upper hole forward and up a little:viewtopic.php?f=14&t=32941&p=129673&hilit=hole+rudder#p129673
Do you have adjustable upper castings, and is the plate as far forward as it will go? If so, I can't imagine how you're not getting enough forward rake. As for the set screw in the lower catings, just remove them or cut/grind them flush...they don't do anything useful. As BigWhoop posted in a similar thread earlier this year, they are for adjusting how deep you want to punch a hole in the front of your rudder blade!
Good luck, man!