I am in Morocco, so watching videos is tedious.
I found the top 2, full length fiberglass battens too stiff for light to moderate winds. I spent a lot of time playing around with Maple, making them of various thicknesses and tapering to thin from a few inches aft of the leading end back to about 1/4 way aft. I am not usually OCD, but when it comes to sail shape, bah, even the rest of the boat, I am a fanatic. I am pleased with the result. The amount of bend can then be adjusted by the tension applied by the Velcro strap holding them in. If you want more info I can post pictures when I get home.