Someone gave me this formula a long time ago and I'm still using it: Take a thirty-foot Hi-Speed Hi-D shooting taper of the rod's rated weight, cut it into two lengths, twelve and eighteen feet long. Cut a fifteen-foot length of floating line, one weight heavier than the the rod's rated weight (level line works just fine and is pretty cheap). Get a 100-foot spool of floating running line (Cortland or SA, .029 to .032 diameter). I use braided mono loop-to-loop connections to make changing the head easy and because the front ten feet or so of running line will eventually begin to wear (I put loops on both ends of the running line and swap ends when it begins to crack and peel). The reason for the fifteen-foot belly is to smooth out any tendency to hinge and this rig casts much better than any of the Teeny lines. I work the head and belly out beyond the rod tip with about two feet of overhang, double haul and let 'er fly. I agree with Salmo, for dry fly fishing (or greased line) a full floating line on a s[pare spool is the way to go.