From a Twitter discussion that happened after I posted my Petzl Elia Review.

In chronological order:

Chicksclimbing
 
This review of the Petzl Elia helmet from @rockgrrl is really making me want to try one! http://ht.ly/2SXql #climb

AlpineInstitute

@Chicksclimbing Right after I 1st saw the Elia, I helpd in a SAR where the vic wouldn't have survived if the ponytail spot had been exposed.
38 minutes ago via web in reply to Chicksclimbing

rockgrrl

@AlpineInstitute What was the situation?
32 minutes ago via web in reply to AlpineInstitute

AlpineInstitute

@rockgrrl Sport leader fall, foot behind the rope, flipped upside down and crushed the helmet right at the ponytail spot.
30 minutes ago via web in reply to rockgrrl

rockgrrl

@AlpineInstitute yowch! I wonder if a Half Dome would have helped, I'm gonna measure the difference in rise on mine
29 minutes ago via web in reply to AlpineInstitute

rockgrrl

@AlpineInstitute ah just realized, the person was NOT wearing an Elia, I'm still going to compare my helmets as it's a good pt
26 minutes ago via web in reply to AlpineInstitute

AlpineInstitute

@rockgrrl The guy was knocked unconscious, but woke up and was helied out. I don't think he would have survived if that spot had been open.
27 minutes ago via web

rockgrrl

@AlpineInstitute I noticed tho if I wear a ponytail with a regular helmet it tends to push it forward... which would then expose my neck
25 minutes ago via web in reply to AlpineInstitute

AlpineInstitute

@rockgrrl No helmet's perfect. They're all going to have downsides. I just think the rope behind the leg accident is somewhat common.
20 minutes ago via web in reply to rockgrrl

rockgrrl

@AlpineInstitute Agreed, took an upside down one myself, tho the helmet scraped midpoint, just took a comparison pic of 3 helmets will share
9 minutes ago via web in reply to AlpineInstitute

Comparison pic of the back of three helmets:
From Left to Right Petzl Meteor III, Petzl Elia, Black Diamond Half Dome


It seems that the real ponytail enabling feature of the Elia is not the "cut out" of the helmet but rather the new suspension system, instead of having straps cut across the back of your head, the bracket goes in a U loop, allowing ponytail access.

Usual system:


Elia's OMEGA system: