Carol - Very nice work as always.
As you may recall, I've done a lot of dry sack testing myself, mostly in connection an article published on my website last year entitled "Keeping Your Critical Gear Dry". That article was also recently updated with my own test results of the Sea to Summit Ultra-Sil bags, which I too found unacceptably leaky.
I must say, in fact, that I've mostly given up on any dry sack whose seams are sewn and taped. That construction technique, irrespective of manufacturer, just doesn't seem to hold up to real world trail use and always seems to eventually leak. Instead, if I bother to carry dry sacks at all, they must now be built with welded seams.
My current lightweight favorites are the Camp Inn basic nylon dry bags that weren't included in your review. In wet conditions, I often carry two: the first is the 10-liter bag that holds mostly trail clothes and, if necessary, camera gear in the event of downpours or river crossings. It weighs 3.2 oz.
The second is the 19-liter bag for my sleeping bag and camp clothes. It weighs 4.5 oz. (the 10-liter bag is not quite large enough for these items).
I also like the fact that the Camp Inn fabric coating is thicker and hardier than on most other bags. It's also a lot more slippery, so gear stuffed into the bags slides in more easily. So far, these bags have held up very well. Though there are slightly lighter bags available, most just don't get the job done, IMO.
I've examined the WXTex Pneumo bags you reviewed and they appear to be well made. Because of the way the top is designed, however, they're not as easy to load as the Camp Inns and the interior waterproof coating is a bit sticky, which makes it harder to slide gear into them. They're also heavier than the Camp Inns.
Further, while the two-way purge valves on these bags are an interesting idea, I think they could also become a liability. The positioning on the sides of the bags would seem to make the valves vulnerable to breakage. I don't know, however, if anyone has actually experienced such a failure, so perhaps I'm just being paranoid.
Anyway, thanks again for an excellent article.