The non-slip mono knot in Lefty's book is one of the few knots that tests almost 100 per cent knot strength. Using a uni-knot, the break point is considerably less.
Curiousity question: the uni-knot slips under tension (ala hookup) and comes tight to the hookeye. Is that important if you keep tension on the line to insure that the hookset remains in place?
The non-slip mono is an excellent knot to use for maximum free fly movement with the advantage of knot strength. I agree in light tippet applications that a double line clinch improves knot strength, and the same applies to blood knots tied using significantly different diameter material, e.g. .020 connected to .010.
Another knot that is used for added strength is doubling a bimini twist with a double surgeons knot for a loop or albright knot to a bite/shock tippet.