I've wondered about this often. Assuming rain isn't too terrible, is it safe to leave the vestibule partly open, and cook in that? This will be using an alcohol stove. I already worry about breathing in the denatured alcohol fumes when cooking outdoors, and not sure how much of these fumes escape the vestibule when you're halfway covered. Also, I guess that the wild flames of the alcohol stove could also be a concern, even when using a windshield.