Just set it up to AHPC's tuning guide and forget about it for awhile (time to go sail and learn about your boat). In the A-class, the mast rakes have been coming back and typically the limiting factor is the mainsheet going block to block and getting under the boom. It seems like in most of the A-class designs, more mast rake makes the rudders more effective and helps keep the bows up in breeze downwind.

Good luck and have fun with your F-18.

Bob Hodges