There are fabrics lighter than 1-1.5 oz/sq yard if you're looking to go as light as possible. Some that I'm aware of are:
- Nobul fabrics from Titanium Goat. These are 7D-10D
- Momentum fabrics from thru-hiker
- 20D nylon taffeta from Outdoor Wilderness Fabrics (owfinc.com)
I just made a quilt with the 20D taffeta from Owfinc. It's spec'ed at 0.9 oz/sq yd. It feels slightly more substantial and is more opaque than the Momentum 90 I got from thru-hiker. I've worked with all three of the above and they all have DWR, are surprisingly (for me) water-repellent and have a slightly stiff hand.
I've also worked with 1.1oz nylon ripstop (uncoated) from either owfinc or Quest Outfitters. These are 30D. Has DWR but I've found it to be less water-repellent than the three above BUT has a softer hand and drapes better. Also more opaque than the thru-hiker Momentum.
Also, FWIW, I made a rain anorak out of the "Hi-Vent DT WPB" fabric from Quest Outfitters. 1.8oz. Super nice drape, waterproof and surprisingly breathable. I just got back from a hike and ended up wearing it most of two days; one day in the low/mid 50's where I used it as a wind jacket and another day that was a little warmer but rained the entire day. My men's 'small' equivalent weighs 4.3oz. I'm really happy with it.