[RWebb]

what mtn.? how high & where?

in the West that would mean some serious shelter; not a so-called summer tent as in the pic above

Quality costs money - and a good mtn. tent - altho no sub. for experience, skills, & a cool head - can mean life or death.

I've spent a fair amt. of time in bivy sacks -- comfy is not the right word.

sounds like insect exclusion is not going to be your problem - you want a good winter tent

you might call REI and ask them what to get after explaining your trip.

set it up beforehand several times - set it up in the dark until you can do it fast ('cuz ya might have to) & seal the seams very carefully