Most anglers throwing streamers for trout or steelhead on switch rods prefer a SKAGIT SHOOTING HEAD on their switch rod. There are a variety of lines to choose from here and these are short heads ranging from 11' - 20' or so. These lines require the use of a running line as well. On light switch rods less than a #6 most anglers prefer mono running line because the light heads tow it out so well. On #7 weight rods on up the running line is less critical because the head weight is great enough to tow it.
The pro's to the shortest heads are that it makes throwing large flies much easier, but it is a bit less stable in flight and will cost you some raw distance. If you are fishing small to mid sized water this is a great idea. Shorter is better. For anglers casting flies long distances to Steelhead and Salmon a longer head closer to that of a traditional Skagit head of 23' is a better choice.