You can use a flashlight on the sail but I still feel more comfortable with a bow and stern light, as well. West Marine sells portables for both. The bow light fits exactly into the end of my bowsprit. I drilled a hole for a bolt to hold it in and it's easily removable.

Go here:
http://www.westmarine.com/webapp/wc...um=236&subdeptNum=235&storeNum=9

West Marine Bow Light Portable