> Roger, are any of the high-tech fabrics such as
> spectra/dyneema or kevlar/aramids suitable for clothing?
Well, those are FIBERS, not fabrics. I make the distinction because how the fibers are woven makes huge differences to how it behaves in a fabric.
More pragmatically, you can buy both nylon, Cordura and Kevlar fabrics at OWFINC. The Cordura is a bit more expensive than the ordinary nylon of course. However, while OWFINC quote a price per YARD for both of the nylon fabrics, they quote a price per INCH for the Kevlar!
So while the fibers might be suitable for gaiters or the seat of your pants, you would have to ask whether you could afford them.
Apart from that, those fibers and fabrics made from them are tricky things to handle, and you would need to use Kevlar thread for the sewing to retain the strength. I have some Kevlar thread, but it is hard stuff to sew with as well. Mind you, when I slashed those gaiters open on the sharp rocks on the Larapinta Trail in Central Australia, I did use the Kevlar thread to repair the tears. It took the abuse at ankle level.
From my experience, I think 500 denier and 1000 denier Cordura or Kodra fabrics or similar may be enough for me.