When used on a quality mainsail, with tapered battens, full length battens add structure to the sail giving the sail better shape and helps sails last much longer. Catalina 27's that are raced tend to have additional roach but that comes with the price that the leech will hang up on the backstay during light air tacks.
Thanks Jeff for responding. Noticed you were in Annapolis; we are on Rock Creek off the Patapsco. We don't race our boat, just cruise the Chesapeake Bay.
We usually sail in relatively light winds as Rob won't go out if the wind gusts exceed 20 knots. If the wind gusts go to 20 knots, Rob double reefs the main sail.
Since we only go out in relatively light winds and since, for the most part, the Patapsco and Bay mostly have light winds particularly in the summer, I would think having more sail area could be beneficial but I may be wrong.
We have never had the leech of our sail hang up on the backstay. Here is a picture of our boat with our damaged main sail:
Very curious to know: does our boat have a regular main sail for cruisers or does it have extra roach?
You mentioned "When used on a quality mainsail": how do you know when a mainsail is quality?
Also, for sailors who are not quite sure what a "good sail shape" actually means, wouldn't it be best to have the full battens so the sail can correct for our lack of knowledge?
Charlene & Rob