Aim is the most important. You don't know how many people I pass and then comment to about how their lights are either aimed at the sky or ground.
I wouldn't recommend putting it on a backpack, hard to position right.
Planet bike sells a nice blinker on a mount that always self rights the blinker. Use a cable tie to attach it to your helmet.
Have the one on the bike going solid and the one on the helmet in blink.