Just wanted to give a completely subjective, unscientific nod to MFC thread, in particular their 8/0 stuff. I've been tying a few smaller foam/deer hair flies recently where I needed something relatively strong but didn't build up too much. Neither Uni 8/0, UTC 70 or Danville 6/0 worked particularly well - Uni often cut the foam and popped when I tried to lean on it while flairing the deer; UTC, being "flossy", was better with the foam, but often separated under pressure (spinning the bobbin/thread and using softer ungulate hair like caribou helped some); Danville, which I love for other applications, was the weakest of them all (my stock is pretty old, so that may have been a factor).

The MFC gave me what I was looking for with a minimum of wraps (and minimum cash output, too!); may have to try it on some smaller Goddard Caddis to see how it handles that. The only problem I've found with the thread is availability - poking around in a number of flyshops in it's home state only turned up a few spools and not too many on-line vendors carry it either. If you can get your hands on some, give it a try; the 6/0 is very nice, too, and surprisingly fine.