I do this every Wed from April to Sept and I have never found a good single solution. I have 2 possible solutions if you have enough wind to fly a hull. If you can time it perfectly, lead the pack and out accelerate everyone to the pin. Now you have clear air and no one trying to take you up. This does not work often. The safe option is to hold back and hit the line at the committee boat with speed. Now you can tack for clear air and go for speed or if the pack leaves a big enough hole, you can foot off and roll them. If you can't fly a hull the best bet is to try to stay in clear air.

NOTE: you realize there is no relationship between multihull and centerboard Portsmouth numbers. What I have found is if I can fly a hull 50% of the time, I win. Less than that and I can't win unless someone does something stupid.