I need a little help understanding the whole switch rod concept. It seems to be like light weight spey casting which looks like a lot of fun. The building kits I have looked at are a little puzzling. You get a 5 wt. blank and then line it with 6 or 7 wt line? Is this just an option to overline the rod a bit like with a standard fly rod or is this a must for it to cast properly? Is there any kit out there made for lighter line weights or does that just defeat the purpose of the casting style? I been studing single hand spey casting and this seems like it could really add to that style of casting.