Thank you koala, I think you've helped me to make my decision - well at least I think I can eliminate the Assos, sadly 'cos they sound like they have a lot going for them. I really don't like shiny lycra, I've retired each and every piece of shiny from my cycling wardrobe, and now go for the matt finish.Perhaps one of my musings might be a tie-breaker. The Assos short is a simpler design, just a few panels, and the fabric is a shiny, high-stretch lycra, very similar to what might be used for bathing suits.
Now the decision seems to be between the 3 pairs of LG's. The Powers sound like they would do the job, but being a shorty, I'm not keen on the leg length. In any event, they are out of the running 'cos TE only has them in XL, and I'll need S. So, it's Alveo with the Ergozone chamois with 8mm thickness in the rear, or the top range model the Airstream with the amazing chamois that looks like a topographical map. As you said earlier, it would really be essential for your sit-bones to line up with the ridges in the back area. I must say, I'm impressed with the style/look of the airstream... hm.. they certainly look the part, and both shorts have the muscle support fabric....
I wish I could afford both...