Take your rods to a flyfishing shop, they will have reels already set up for the various line weights and are usually very accommodating in letting you cast with their reels to match your rod. On another note opting for the higher end line weight helps in loading your rod, however, the taper of the line is what allows you to shoot the line. I have found using ie: 7wt line with a 7wt rod with todays line taper improvements easier and provides improved fly, mending, and line control. As with all advice if you are going to use weighted and large flys dependent on the stiffness of the rod increasing line weight may be advisable.
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My Birthday began with the water
Dylan Thomas