I share your frustration. Last season was my first with the b310 SD and we were getting clobbered by the fleet for the most part. But, I haven't yet replaced the sails which are tired and I was dealing with less than optimum crew. Coming out of the J24 from 30 years of competitive racing in KS/OK/TX/Nationals/Etc that I knew how to tweak for minute changes in conditions, I am effectively starting over. At this stage, for me, it's not the boat's fault. I have upgrades to do and seat time to be had. This thing is like driving a dump truck when compare to the J24. But, she's damn sure more comfortable. ;-)
Something you might consider is straight line testing with a known baseline boat. For example, if you have someone that is willing to test with you, try setting a mark say 1 mile upwind and "rabbit start" with them. Go upwind with them and have them mark time when they get to the mark and you do the same. repeat the test to see if they are matching their number and if you are matching yours and evaluate differences. Might also consider swapping skippers & crew to see if their crew on your boat does better and vice versa. If you have new sails, get the sailmaker to come on board and provide "tech support". Object is to figure out whether it's bad ratings or bad setup and mechanics.
The beauty of the J24 was that every leg of every race was a straight line speed test and you knew all along whether you were competitive or not. Not so with the Ouija board.
Good luck, stay in touch. Happy to share whatever I can. Have raced a lot over the years at OCBC.
