Depends on how paranoid you are about possibly getting hit. There are some recumbent trike riders who light up their trikes with all kinds of daylight lights even going so far as to fabricate elaborate "roll bars" to mount them on. I don't use daytime lights. I always use a safety flag but never used them on my 2-wheeled recumbents. Is that rational? Probably not. Even without a flag, motorists give me more room than on a regular bike. It does have one place where it helps and that is at a traffic light where you have right turning vehicles. Once they pull up beside me, they would never see the trike were it not for the flag.