Alec,
I too am having the same kind of problems. Nigel Pitt gave me some pointers a while back and said that you can't try and point this boat. That big jib just won't do it. "You gotta let the big dog eat". Besides the major points in the tuning guides, I've since found that getting the boat bow down upwind helps a lot and keeping the jib slot open is critical. I've raked the mast all over the place and STILL can't feel much difference.
I've been relatively competitive with the 6.0's I've raced against so far but I too am getting schooled by Hobie 20's around the buoys. In my defense, my sails have something like 1700 miles on them (x-worrell sails at least once and the previous owner and I have sailed the snot out of 'em). However, I have a new set sprawled across my pool table as we speak and I'll let you know how that turns out!
There's a tuning guide on catsailor by Jamie Diamond you might want to look at and you may want to join the N6.0NA forum as well. Links below:
Jamie Diamond tuning guide Yahoo N6.0 group