I am by no means anything but a novice re spey fly fishing. I am learning just like you and this is a very evolving pursuit, always being tweaked with innovations from the pioneers in the field. I came across this link of a steelhead & spey enthusiast from the Great Lakes region. He has a lot of good, solid, basic info for a starting point, realizing that every expert or wannabe expert may have differing opinions. One has to start somewhere. He covers more than lines. His patterns are a bit different than most NW spey flies, but again, maybe something to be learned and added to the arsenal.   

Modern Scandinavian shooting heads resemble standard WF Spey lines only in a reduced length.  So instead of being 55’ to 75’ long, they’re only in the 30’ to 45’ length.  While they may be as much as 40% shorter, they’ll only be about 20% or so lighter, resulting in a line that is fairly heavy for its length.  This characteristic is required to provide an adequate rod loading when using such as short line…….

 Skagit heads are designed as sinktip lines composed of a very thick, very heavy floater belly, often just a piece of level line, attached by a loop-to-loop connection to a sinktip that is usually made up of T-14.  Unlike Scandinavian heads where length is dependent on a variety of factors, Skagit heads lengths are strictly a function of rod length, being typically 3 to 3.5 times the length of the rod (line length includes the sinktip, but not the leader). 

http://www.hooked4life.ca/glsteelhead/Scandinavian_and_Skagit.html