From filming several attacks last year with a GoPro on my helmet pointing backwards, most magpies came in fast from behind and slightly to one side, aiming for one of my ears.
So this year I've re-positioned the zipties on either side, pointing backwards, with the flashing lights as low as possible. These are push to operate, so when entering a known swooping area, I can reach up and turn them on.
It seems to be working. I was swooped this morning, but the magpie veered off and gave up.