was researching fly lines for the Shadow 2 and ran across this from the rod's designer, Pete Erickson, others might find it interesting as well:
"Just bouncing around through some interesting threads here and I came across your question about line size/type for your new rod . Just to clarify, I'm not posting to promote Shadow rods, but, since you've already ordered it I assume it is ok for me to give you some line advise for the new Shadow II 10ft 3wt.
Before you go out and purchase a "nymph" line for this rod, a couple of things to consider--unlike the old Shadow PE's, the new Shadow 2's are more accurately matched up with the rod's listed line designation.
The Shadow II, 10ft 3wt matches up well with a standard 3wt WT or DT line...it lists as a 3.5 designation, whereas the old Shadow PE 10ft 3wt designated out more towards 4.9, meaning that it was better suited for casting a 5wt line at 30 feet.
Choosing a line for a particular rod is always very subjective and even situational. The Shadow II's are what I call a "hybrid" rod, meaning they are designed to throw a dry fly, Euro nymph rig, and even cast a team of wet flies. I prefer to load mine up with standard WF or DT line that matches the rod's designation--in this case a 3wt; that way I can take advantage of the fact that this rod throws a nice loop for dries but also I can immediately switch over to making lob casts with a Euro-Nymphing rig all with the same standard wf or dt line.
as far as line manufactures go--they all make solid standard wf/dt's ...so find one you like
have fun---it is a fun rod
cheers