For those of you that have made your own bivies, how do you prevent condensation? I'm thinking of using silnylon material, but I'm wary of its lack of breathability. My current blueprint has poles that will raise bivy material above the user so that you and your sleeping bag won't be contacting the bivy walls. I've also added some side vents, and I have a bug net that can be used by unzipping part of the top bivy layer on dry nights. Any recommendations would be appreciated, as this will be my first major MYOG project. Thanks!