Re: Question regarding oversize rod for smaller flies?
Small flies--like how small? I fish #16 & #18's on occasion with a 7wt rod for GL Steelhead and don't find that too much rod for the flies at all. More important that rod provides a good balance of being able to feel the fish and giving me enough power to get it to hand without working over the fish too badly.
It sort of makes sense that a rod with a heavier line weight is easier to cast, there is more mass there so casting may be easier as he describes. Having said this, it could also have to do with what line he has paired with the rods. Sometimes a mismatch of line makes it harder to get line out there as you've alluded to in your comments regarding over/underlining. The rod's action & brand are a variable to consider that could be impacting the ability to cast with a 4 or 5. Then again, so is comfort level and skill.
I'm in agreement, that too much rod for smaller fish can lessen the enjoyment to some of us. Another thought is that a heavier line may create more drag or be more likely to spook fish on some waters, like spring creeks. On the other hand, a long leader can help to lessen the spook factor. It's not necessarily the tool, but the angler. If he's comfortable with a 7, go for it.
For years, anglers fished with one rod and that did the trick just fine. Marketing has got the best of us and suggests that we "need" rods for various scenarios. I own way more rods/reels than I'd need in a couple of lifetimes, I know I could easily pair down my lineup but collecting and fishing with variety is fun!
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