I’ve a reproduction helm, and for the life of me, when I attempt to wear it capways, it just wiggles everywhere.
That's because you're trying an artistic convention in real life, and that works about as well as trying to imitate the weird stuff films get up to. u/Iphikrates has a post explaining further, but as always, if anyone would like to write more about this matter, please don't let this post stop you!