Cutting it in a pinch yes, just a touch on either side but otherwise it may be too stiff for the sail. Won't be able to sell it either after. Also the curve will be altered some, though not a big deal if it's just a little bit.
I would try to pull it apart:
Oh it's the extension, then it's easier as it's more résistant to heavy clamping. You can dip it in hot water then in ice cold water.
Check if it's oxidation what you can do to break it apart with things like penetrating oil.
