I am using Rio powerflex at the moment, I've been quite impressed with it so far. Not too stuff, not too subtle, easy to tie and seems to have good knot strength.I tried fulling mill, drennan double strength, rio powerflex and stren fluoro, among others. None as good as Maxima green or brown. And it knots up a treat. When leaning on a fish with anytjing else i worry. With Maxima i am always confident. 10lbs for smaller stuff, 15lbs for bigger flies on sinking lines. This is a pretty agricultural approach, but it works.