Helmet suspension & straps

SO in doing a little poking around on armourarchive.com, it sounds like general consensus is that historically helmets didn't have chin-straps, they were just a good enough fit over your arming cap/coif/etc that they stayed in place.

Obviously, when buying cheap (used and Ebay) and/or renting out to unknown actors, that kind of fit isn't going to be achievable often. SCA also requires chinstraps, so there's plenty of other folks out there needing to put some kind of helmet retention device on there.

Anybody have a system they like best? I've found with helmets that don't come down the back of the neck or wrap around much, that a single strap just creates a pivot point, and the whole thing can still flop around over your eyes, back up on your head, etc... so I've been working with a system where it's a bit more like modern bike-helmet straps: If you look at it from the side, there's a Y shape, with your ear in the middle of the fork of the Y. To make 'em more adjustable, I've been making one strap more forward, then adding a hole further back, and using a tie stitched on to that strap at the bottom and passing through the hole in the helmet on the top. That lets me easily adjust it tighter or looser, more forward or more back a bit too.

Worked well enough for the gladiator gig I posted about already. Using that on some medieval helmets for a production of Macbeth I'm gearing up for now.

Still not the most comfortable system though.

I've seen some that cup the chin instead of passing under it, but I'm concerned that might hinder actors giving lines.

Thoughts/experience?