what matters most isn't putting a light on each pannier. It's having a bright rear light and an outfit that helps to define your human shape. Wear a reflective outfit and put a PBSF on your helmet/bike. If you need more than that then put more PBSF on the bike or have a generator light with a dedicated tail light. Complaining about panniers not holding a tailight at the right angle is dumb given all the other options.