I see. Just in the top photo it looks like there is elastic running around the back of your head, on the outside of the hood.
Arc'teryx is a great brand. I have a couple of jackets by them, and in general, its very rare that i see or use an outdoor product and I think, there is nothing I think could have been done better. I actually have an arc'teryx alpha sl shell, which is one of the ones with foam in the waist. it is handy under a harness, but the jacket also isnt as long as yours. that jacket is on its last legs though, so this winter I plan on making a replacement. really light eVent or medium weight Pro Shell is the question.