Think you need to take a step back and think about just how your going to use it , if you're going to be using for mainly days then your going to be sitting up in a decent chair and going to need some head room, sitting on a bed chair is not that comfortable . Think that a brolly type would be to low for you to sit under , the ribs inside even with the smaller bosses still take up a fair bit of headroom, where most of the bivvie systems have the frame work on the outside..