With your boat on dry land, put your mainsail up. Measure the distance between your bows. Now crank the mainsheet. Measure the distance between your bows again. There will be some difference, but it should be minor, maybe about an inch max. A big difference indicates things are getting weak.



Other possibility - your headstay or bridle is coming apart, maybe underneath the plastic coating.



If it's the stays - replace 'em!



If it's the hulls, well... You'll have to figure out if they are mostly safe, just starting to flex. If so, maybe a bridle foil like 5.5, 5.8, and 6.0 (or something like the H-17 sport pole) would be worth a try. It would help keep the headstay forces from pulling the hulls together like the normal bridle wire setup does.