In my case... the 6 wt is easier to cast than the 5 wt, so theoretically, if the 5 wt should be easier to cast, as you say, then it is probably the rod, not the line weight, that is giving me the difficulty. As far as trying different line weights on the two rods, I was just experimenting to see what difference it would make. However, I will admit that I will probably use whichever line casts best for me, regardless of whether or not it has the same designation as the rod. Thanks for your feedback.