Iceman
Mantis is okay but has a tendency to rise up from the river bed if you don't peg it down with rig putty, this can put wary fish off.
Silkworm is soft - very soft! It can tangle just by looking at it. Its great for still waters but on rivers I find it too much of a hassle.
I suggest that you look for a 'sinking braid' these are always a bit thicker than the others but will settle nicely on the river bed and give you a much better presentation, I'm using a Wychwood one at the mo. but I can't remember its name.
If you do use a soft braid its worth running superglue down the first 4 or 5 inches from the swivel to stiffen it, this creates a slight boom effect which stops the tangles around your lead.
Hope this helps.
