great information coming together here, thanks all, keep it coming!
I'm thinking I'll have to work around the limitation of 60" width. It's not ideal, but manageable. It's hard to me to understand why such a narrow width has become de facto standard, but that's what it seems to be.
I can not live with a colour that stands out though, so that requirement has to remain. Being semi-translucent to me almost seems to be an advantage, because it lets some of the colours behind and underneath it shine through, which helps with blending into the environment (unless you have a blaze orange quilt or sleeping bag, haha). Some of Ray's colours do that, too. Also, there is more daylight underneath the tarp, which is nice.
Don't know how heavy exactly Ray's sil-nylon is, because he states "oz/yard", and I'm not entirely sure if he actually means by yard, or by square yard. He states 1.3 oz/yard, if he actually means oz/yard, at the width he is selling it that converts into app. 2.2 oz/square yard. If someone could clarify that somehow, that would be great because then I would have a number that I can compare my possible candidates with.
Whatever the weight of Ray's material actually is, from own experience I can say it's strong enough for what we do, but I admit I wouldn't mind adding some 20% strength or so because (only!) in very high winds (read: walking is difficult), his material does stretch a little too much to sleep peacefully; you can see it by just looking at it before you dive back into the cover underneath after fine tuning some pegs and lines in the storm. It never showed any visible damage the next day, and no permanently remaining stretch either, which is fantastic, but I'd just like to know for sure that it will survive while we are in the storm, instead of having to lie awake throughout the night ready to improvise an ad-hoc makeshift shelter from our groundsheet any second in case the main shelter blows. It would not be very enjoyable to have ourselves and all the gear exposed to storm, rain or even snow from one second to the next. A couple times I thought it might happen, but it never did. I am impressed with what Ray's material has done for us, and we definitely take the tarp into situations that are pushing it for tarps (and probably for most tents as well) - but it would be good for what we do to have a wee bit extra strength. It would just allow us to have nicer dreams on those nights.
It's a shame that Ray doesn't offer any more stealthy colours, especially since he promotes stealth camping so much. If I could buy his sil-nylon in a truly stealthy colour, my quest would be over, and I would simply buy from him again. The performance of his material was so good for us that whatever we choose, we run quite a risk of being disappointed, even if we use something slightly heavier. Weight is no guarantee for performance.
(Disclaimer: While we had extremely positive experiences with Ray's sil-nylon even under adverse conditions and in exposed places, note that of course we pitched very low in these storms, with the ridge maybe mid thigh high or even less; we used all pullouts and lines; had additional extra pegs in important places; and fine tuned the tension all around very carefully. I would definitely not recommend to anyone to try tarping (nor tenting!) in such conditions unless they have significant skills and knowledge in tarping, and in bushcraft in general. Even the most expensive shelters can fail. If you would be in a life threatening situation without your tarp or tent which you could not get yourself out of due to lack of gear or skills, in an ideal world, you shouldn't be there in the first place in my opinion. Extend your limits by learning systematically and carefully at the same time, step by step, and you will learn heaps, be safe, and live to enjoy another trip.)
A brief idea: I think I have some leftovers still. If they are large enough, if anyone wants to test Ray Jardine's sil-nylon, just give me your address and how large a piece you need, and I'll mail you some. I definitely also have some of his PU nylon left over as well (used it as a hard wearing and non-slippery floor in another project). Of course I can't guarantee that it's still the exact same sil-nylon that he is selling today, since I bought it years ago, but he never said anything on his web page about having changed materials, and I think he probably would if he did.
To be continued...