The Ultra 20 circa 2009/2010 (roughly) used 9.5oz of down and quite light shell fabrics. This quilt was called the Ultra 20 and weighed about 19oz.
Around 2011, GoLite replaced it with the 'Ultralite 3+ Season Quilt' which was 24oz. This quilt used more down (12oz) but it also used heavier recycled fabrics, so the weight gain was split between the extra down and heavier fabrics. The extra down was needed to get it to a true 20F (-7 C) rating, while the heavier fabrics was a bit of a bummer unless you prefer recycled stuff (to me it's cool, but not worth the 10% weight gain).
They're both good quilts. The first one would be better for you, as you probably don't need 12oz of down and of course the first one is lighter.
I was using the GoLite Ultra 20 (19oz one) for a couple years and it was great, but eventually I decided to splurge on an even lighter quilt with the lightest fabrics (i.e 7D nylon) and best down (900FP) so I had a forum member (Billy Goat aka Virga Outdoors) make me one. This quilt uses 7.6oz of down, so it's rated to about +3 C, but I can take to about 0C with some down layers and I've even used it in a snow cave with good success in the winter with down pants/big down parka.
'Rediculously Narrow' is a bit tricky, as you can't just look at the widest point of a quilt... you really need to also look at the taper to see how it will fit. I find you need just as much girth around the hips as you do around the shoulders. My BillyGoat quilt is about 50-51" wide at the shoulders, but it doesn't taper until after the hips so you still have this much girth at the hips which is good. The Katabatic quilts are claimed a smidge wider at the shoulders (52") but they taper to just 42" at the hips, which I think it where the girth complaints come from (I haven't used one). I'm 5'11, 165 lbs and I find a quilt needs to be pretty darn close to 50" around the hips for me to be able to wrap up nicely in it. I'm often a side sleeper, which is where these girth requirements come in. If you're only a back sleeper then a regular Katabatic is likely fine....otherwise I'd only look at the 'wide' ones.
Zpacks quilts/bags are 56" at the shoulders and hips, so nice and generous for a quilt, but a bit tight if you have it zipped up into a bag. My internet is sucking right now, but I think EnLIGHTened Equipment/Tim Marshall has a few different options in this regard. Side sleepers will want decent girth, while back sleepers can get away with less.