>>665831>1. how bad is condensation with cheap normal non goretex/event bags, like for example alpkit hunka?Don't own plebtier equipment... No, seriously, I don't know desu. No experience with condensation, ever. Maybe once, but no problem
>2. do down bags work in bivis or won't they work because of condensation and it is better to bring a synthetic bag?Haven't had problems using my Cumulus down bag. Not "dry-treated" down, either.
>3. is there a good buy option for a tall size breathable bag?Sry, too much work to Google for you, and I don't really know about a lot of options outside the UL world, and they're... slightly pricey as a general principle.
Try
http://www.ebay.com/sch/i.html?_nkw=lightweight+bivy>4. mat goes in our under bag?However you like. Scientists argue.
>5. piss bottle obligatory?No, why? Just go out and piss. Unless you really like pissing inside tents in general?
Pic related, my Katabatic Bristlecone bivy under a HMG square tarp.