I use the adventure medical kits bivy, about 8.5 ounces. It serves as an emergency reflective heat barrier if I ever take a dip and everything is soaked, a water proof ground cloth, and when necessary during nasty storms will keep my bag from getting soaked. It also serves as a water proof stuff sack for when my sleeping bag is dry and ready to be put away.
I cut it down and added a zipper to prevent bug problems, put struts into the feet of it for ventilation that tie out with small 0.1oz stakes and masons line to add ventilation, and added a beak to the foot box that stakes out so I can use the netted ventilation window at the bottom. The rest of it just lays on me but I find if I just prop up the inside with a stick or tie an inflated platy bottle around my waste it stays off my sleeping bag pretty good, again promoting ventilation. I wear the OR bug net w/ring in it over my tilly hat to prevent the netting from laying on my face. I use a sleeping BAG, not quilt because quilts don't work for everyone believe it or not.
Here I am happy as a whistle with my multiple use gear. I just don't use the bivy unless condensation becomes a lesser worry than a poorly pitched sight or nasty nasty storm. This is the thing about bivy sacks. People are supposed to use them as a secondary shelter and I see folks around here going to them as primary. We might as well make our quilts out of thin silk if this is the case. Quilts and bags are made to stand alone in near direct rain conditions for sustained periods of a couple hours. There is no reason to wear that bivy if you aren't getting hit with rain drops imo. Even my super cheapo marmot down bag (under $180) can resist dew and spin drift/condensation for hours and hours on end w/out making me miserable. Sometimes I zip my wind shirt around my foot box to prevent wetting out or throw up an umbrella, scraps of fallen brush. my backpack pad/sleeping pad… or whatever I can find. I mean its all about improvising with a minimalist tarp and conditional use of a bivy for safety concerns to me. Eventually you learn how to pitch the tarp, what direction to face it, and where to pitch it. Once this happens a tiny tarp and wind shirt can keep you dry in anything you can encounter in 48 states.
Tents have their place too. My favorite shelter for rainy rainy days is goretex. Goretex is considered a DON'T around here but I feel differently when I'm wearing it the entire time. My goretex bivy w/pole and stakes barely weighs over 20oz and keeps me 100% dry no matter what. If it is raining more than 2 hours a night I don't see the point in going light. Its just miserable.
The same goes for tents and bugs. My tarptent is great with the bugs, less experienced friends that go occasionally with me, and for the ladies. Bugs just aren't tolerable to me at elevated levels and on any level what so ever to my friends/girl friends. There is no point in them suffering because their packs are still around 12lbs base weight with tents and a gallon of bug spray. It is nice to have a tent for extended trips with friends too because they may be tired or simply not want to deal with the bugs all the time, again a retreat for the less experienced outdoors man at any time of day is good to have. I've tried to set my tarp up for people in these situations and it does more harm than good imo. Morale is important! We are out there to have a good time after all.
My dogs are another example of this. My shepherd doesn't care how thick the bugs are its of no concern to him, for some reason he is invisible to biting flys. My shephered/border collie mix is another story! Every black/horse fly in a 5 mile radius will find her and be out for blood. She can't even go on some trips with me, but when she does go I make sure to take the tarp tent for her.
If you want to save the ultimate in weight, get a poncho tarp. This will weigh something like 16oz total for rain gear and shelter. I enjoy leaving my rain gear at home and using the poncho tarp sometimes, other time more harm than help. I'm stubborn about it though and love the feeling of shedding 2lbs so I understand where some people are coming from around here with the one solution fits all ideal. Just keep in mind that it isn't that way for everyone and this is why there are so many options out there.
I also treat my bags with car wax before I head out. This modern car wax w/polymer blah blah blah technology is a life saver. It prevents UV damage and works 10x better than any fabric sealant I use (except for the expensive sail sprays at the boat shop). I've had good luck with meguiar's, be sure to use the stuff that IS NOT A POLISH too. In fact, just don't do this. I ruined a lot of stuff figuring it out. Go to the boat shop and buy the sail stuff its safe on nylon. People that complain about their modern nylon shelled bags wetting out either need to a.) learn to maintain them or b.) buy a new one every year.
The golite poncho tarp w/bivy or the SMD poncho tarp w/out bivy are both great options. Both need assistance from an umbrella or wind shirt from time to time but nothing you can't handle with a little practice.
So, in short. Tent for bugs, goretex bivy for constant rain, tarp for everything else, poncho tarp for when I am stubborn.
