Have you slept in a bivy before? If not can you borrow one before you buy? Despite the practical advantages they aren't for everyone .. possibly including me. I found that a flat / non-hooped bivy triggers a kind of claustrophobia I didn't know I had. I freak the "f" out when that mesh lays down on my face and I perceive air restriction. OTOH I use a hooped bug bivy in summer and fall with no issue so the trick is finding the sweet spot in between. I haven't yet. My notion is a bivy with a hoop over my head and preferably over the foot .. ideally with a ridgeline .. and optional unzip at the foot for air flow would be pretty ideal. The only one I've found that fits the description is heavier than I want.
If you don't have any issues with breathing in one then TiGoat makes some pretty nice stuff. Raven Omni would be my first choice.
Tom
