After fifty odd years of cycling for both leisure and commuting I can say that cable ties only serve to make you look like a porcupine and do not prevent swooping, only contact. Beak snaps are still prevalent and dangerously distracting.
I can concur with the behavioural ecologist however who stated recently that maggies will avoid direct eye contact and immediately curtail their desire to swoop if they think they are being looked at. I have employed a LARGE pair of plastic moving eyes on successive helmets for many years and can say that I have not been swooped in that time, I have noted their shadow as they begin their swoop out of the sun but they immediately turn tail and fly away. If I think they may be more aggressive than usual I shake my head, the eyes move and again, no swoop.
I would not argue that to a magpie's perception, this looks like a fairly intimidating face.