So I'm intrigued to make a light weight vest and I have Seattle Fabrics in my backyard (so to speak). I went down there today to check out insulation and was comparing PL1 and Thinsulate. The Thinsulate had scrim on both sides and looked really easy to work with while PL1 only had scrim on one side which means I'd have to quilt it myself. Since I'm learning to make MYOG and I'd like a vest under 4oz which would be better? I'm not sure how to compare them for warmth bs weight either. Any tips?

Thinsulate is heavy for the amount of warmth, it's good for gloves

One is probably the best insulation per weight, but you have to quilt it - I forget - 8 inches x 8 inches in both directions?

Primaloft Sport is better than Thinsulate, not quite as good as One, requires less quilting, sold by Seattle Fabrics - I might use that

You're going to be more like 8 or 9 ounces for a vest

The liner and fave fabrics are about 1.5 square yards each, total 3 square yards, 3.3 ounces for 1.1 ounce nylon, the lightest SF has, plus One or Sport are 3 oz/yd2 so that's another 4.5 ounces = 8 ounces total. Plus a zipper?

Jerry-
I guess you're right about the weight. I was thinking of maybe using that stuff they make vails out of but I heard that primaloft will migrate thru fabric like that. Think I could get by with only using the scrim on one side and using nylon only on the outside of the vest? I just wonder if the scrim will get caught on my baselayers and be ackward. I was thinking of maybe using Velcro instead of a zipper or maybe something else but I'm still undecided.

All synth insulation needs to lined on both sides. The scrims simply are not durable enough to withstand even the most delicate care. If you want bare minimum weight you can use silk but you lose wind resistance and some durability (although durability is a debatable subject).

PL1 has about ~15% more insulating value per weight than Sport (according to Primaloft's specs) which may make up for the extra quilting necessary.

Also does Seattle Fabrics have the latest version of PL1? Primaloft did a "free upgrade" a while back where they improved their production process that gave a healthy boost to the clo value of all their insulations. I've contacted Seattle Fabrics to see if they've received any of this "new" PL1 but they've never responded to a single email I've sent them (which brings up potential customer service issues, but that's just my own preferences on the matter).

Check out this vest on my blog: http://lightaspossible.blogspot.com/p/clothing.html
The total weight is 87 grams(3.1 oz). I used primaloft sport (60g stuff). It's really warm, and perfect for under a jacket. If you need any tips or info, let me know.

Sam- Your vest is what gave me inspiration to try and make my own! I really like your basic design approach and of course weight savings.