shelter musings after some experimentation

I think practice is required with tarps, particularly with getting your pitch suited to your needs.
From the sound of things, you probably had that 8×5 Oware tarp pitched just a bit too low, and you couldn't move around underneath it well. I'd bet that if you pitched it six inches higher, you might have felt differently. Plus, you have the waterproof bivy, so you should be able to handle some rain spray if it blows in.

The tarps will let spray from side-blown wind get on you unless they are big. If you want small and light, you had the right idea with the bivy and smaller tarp. You just need a light bivy sack instead of that 1.5-pound one.

My conclusion is that for a small 5×8 tarp like my ID Siltarp, a waterproof bivy will help in rainy conditions, but to use a waterproof bivy, it's either heavy or it doesn't breathe(or both!). By using a vapor-barrier-layer(VBL), you can use a waterproof bivy that doesn't breathe because your VBL stops your body moisture from getting out to soak your down bag.
A cheap VBL inner bag can be made from a AMK Emergency Bivy made from "space blanket" type material that only weighs 3.5 ounces. Then, you can use another one on the outside of your bag as the waterproof bivy. And your bag won't get soaked from the outside, or the inside, because of this system.

You vent your sleeping bag and/or inner VBL bag as needed, so that you don't sweat. I know it feels different when you first use it, but you get used to it, and it really works. Mostly people use it in cool weather, and it's not ideal for a summer night at 80 degrees. But on a hot summer night, you can probably just use the space bivy, and forget the down bag with that heat.

When you use a VBL system like this, you have warmer nights, and your bag lofts well because it isn't damp from body moisture or rain, and it's cheap.
If you want to buy more expensive stuff, you can do that because it's out there. But you don't have to unless you want to.

Of course, this is all based on your personal preferences, and what you might be willing to spend/put up with. I haven't made any significant purchases recently, and even thinking about the cost of a cuben tarp makes me feel slightly dirty. I own three shelters: a four-pound two-person tent for car-camping/float trips, a 6×9 sil tarp, and an 8×10 sil tarp.

It seems that you have answered your own questions, as you have stated your fondness for the tarp aesthetic AND you successfully weathered a storm under one with a friend (with no bivy mentioned). If you are alone under an 8×10 you most likely don't need a bivy unless you want a bug net, and if you're cozy with your partner you may get by just fine sans bivy while sheltering two. If you decide to own an additional solo tarp/bivy system, then yes, you'll want a much lighter bivy. Seems like you'd be much lighter with an 8×10 alone than with the small tarp + heavy bivy system you mentioned!

I would recommend more practice with a tarp: you will only improve. If you want to try different sizes, cut them out of plastic or buy/use the woven poly hardware tarps for a while. Cautiously and humbly I'll mention that I doubt you'll be needing to dig any trenches with more practice in site selection. Alternatively you might try a pyramid/alphamid/TrailStar or other shaped tarp, but I have no experience there.

Edited to add that I did come across that article in BP'er, and found it as a whole a decent piece of writing. However, the author seems to have misused his tarp three ways in three nights, after which point he dismisses that shelter category as a whole.

a small tarp is definitely a spartan affair, I used a 8×5 poncho-tarp for several seasons along w/ a light bivy (7 oz)- no way I'd consider going with this tarp w/o the bivy (even with 0 chance of rain, it will still rain in the mountains! :) )

I have recently gone less spartan and moved to a small pyramid (MLD solo trailstar)- this move made me carry raingear, now that my shelter isn't doing double duty (btw breaking or setting up camp in the rain w/ poncho-tarp- sucks!) add 7 oz; the solo trail is 4 oz heavier than my poncho-tarp, but while I've gained roughly 11 oz the extra room to store my gear and even cook has been worth the trade-off. After several nights in the pyramid, my next trip I'm living the bivy at home- I don't think it will be necessary for – if it's buggy I'll bring a head net, if this proves out then my total gain is only ~ 4oz

I certainly don't regret my experience w/ a small tarp, I learned a lot and am hanging onto it because I just might get the urge to go SUL again :)

the bottom line is if you want the very lightest load possible, then one had better get comfy with the idea of a small tarp- if not, then there are certainly other viable options

Thanks guys, very helpful.

Joe over at ZPacks.com offers an 8×10 cuben tarp that weighs just 5.2oz, but in cool, wet conditions wouldn't I still need a bivy sack to protect my down bag from condensation?

I've never used a bivy sack but it is my understanding that a bivy creates it's own condensation issues. A single walled shelter does not mean you need a bivy and a tarp should have less condensation issues than a fully enclosed shelter (more ventilation).

So I think to answer your question, a bivy is only needed if you think there is a chance rain could blow into your shelter and get on your bag. A bivy is not protection against condensation.

If you use a vapor-barrier layer(VBL) as I described above, there will be no condensation from body moisture to worry about. It will all be contained inside the VBL next to your body, and if you vent correctly so you don't sweat, there will be no noticeable moisture inside the VBL either, and you won't be too warm or too cold.
If you have condensation on the underside of the tarp from your breath, that could happen. A bivy would then protect your bag from that moisture and also from rain spray.

The VBL conquers the condensation problems. It takes some getting accustomed to it, though. The better you understand how it works and how to use it, the better you will like it.

>the author seems to have misused his tarp three ways in three nights, after which point he dismisses that shelter category as a whole.

I went back and read that article. You're so right, 3 times he screws up then blames the gear. Funniest part? Afterwards he notes that "two bivy sacks weigh as much as a tent". Just… wow.

"I have recently gone less spartan"

I'm going back in the opposite direction towards bivy/tarp; seems like I'm never satisfied. LOL

After my last trip, I'm really beginning to realize how much I dislike hanging around camp. I was pulling in after a long day, setting up my MYOG tarp tent (with bug netting), and then what?

Now, don't get me wrong, when I'm car camping with family/friends, it's an entirely different affair: drinks, campfire, cooking, socializing, etc.

But in the Sierra, you can't have a fire above 10-10.4k, so there's really not much to do if you're not actively hiking, exploring, fishing, etc.

So, I'm going back to a DRW (but not water proof) bivy that is easy to deploy and has a very small footprint. (Read: set up away from established campgrounds.) With proper venting, an M90 shell provides enough ventilation to avoid condensation issues. But because it's not water proof, you need to take a small 9×5 tarp (sil or cuben) in case it rains.

I agree about drawbacks of the poncho tarp approach. I never try to combo my rain gear & shelter. I have a nice 8 oz rain shell that I use in conjunction with a MYOG silnylon rain skirt.