Christian, I'm a Montana fishing guide
out of Bozeman but manage to get over to the Ruby several days a year both guiding at for personal fishing. The Ruby is a great little river. I am guessing if you booked several days on the Ruby that you are fishing out of a lodge like Ruby Springs that has private access (access can be an issue, but there are several FAS access sites below the dam). I like 4 and 5 wts for the Ruby but a 6 is an all around good Montana rod if you will also be doing some floats on the Madison. Four weights are fun unless the wind kicks up, then they are underpowered. A 5 wt. is probably the all around best rod for the Ruby.