Uh... I don't think I'd recommend those Teak interior battens for a mainsail.. of any type.
I suggest you remove and inspect your sail's battens.. measure the length, width and thickness.. note their shape..and start your search. Batten's come in many different sizes and configurations... here's a reliable source to get you started: Sailrite but don't be afraid to google "mainsail battens" yourself when you know what you need.
Beyond the dimension of the batten -- there are a variety of structural differences between battens of the same general shape dealing with the balance between flexibility, resistance/allowance for bending, damping of fluttering, ability to take "compression" without buckling, etc., etc.
In your Hunter 240, assuming you have the conventional battens, I'd avoid getting too wild. Try calling North, Quantum, or any of the sail manufacturers and ask them what they use.