I have a new Atmos as well, and found that setting it up correctly it was crucial to how well it fit and how comfortable it was. Now it's hard to notice it's even there!
It was important to get the straps adjusted to place teh helmet in the right position, which took a bit of fiddling. Now it sits right, and doesn't want to tilt back as it did before adjusting it.
I also found that the RocLoc system won't function correctly if the straps aren't adjusted right. Now it works fine, and I can loosen or tighten the RocLoc adjusters to compensate for skull cap etc. without a problem.