Meanpressure, It isn't the difference in rod weight that will affect your comfort or ability to cast it all day long. It's the small but significant difference in line weight, coupled with line speed while casting (F=MA) that requires more force to be exerted on every cast, for as many casts as you make in a full day's fishing. That is what you will notice, and specifically, your casting arm's elbow and or shoulder will notice, depending on how good your casting technique is. I see in another thread that you are favoring a tip flex, or stiff, fast action fly rod. As a novice, if your casting skills are imprecise, a fast action 9 weight is an excellent set up for tendenitis or shoulder pain unless you are quite athletic and have no family history of joint pain issues. The point made about going with either odd or even line weights for rod sizes is a good one, except that most avid fly fishers end up with such a large quiver. We end up with one or more rods in both odd and even sizes anyway. I wouldn't worry too much about that in the long run. One thing you got right: there sure is a lot to learn about fly fishing. Sincerely, Salmo g.