Re: Question regarding oversize rod for smaller flies?
Heavy fly lines cast everything more easily and with less effort than light lines. I think that's just fact -- not really up for debate.
I enjoy light tackle, but always carry something heavier for just the reason you mentioned -- I can still fish if wind gets heavy.
Actually, I love my TFO finesse 389 for trout and bluegill, but I usually carry my 9' 8-weight in the truck with it....because in the event that I really need a heavier rod for strong wind...the 8-weight honestly isn't too much (even though about 99% of people will tell you that it is).
And yes, I've fished several times with just the 8-weight and with #14-18 flies. It works fine.....honestly, there's not much real disadvantage other than "less fun playing the fish" which is nonsense to me, and lack of "buffer" to protect light tippet like 6-7x.
I fish the finesse 389 because I enjoy light tackle, not so much because of the advantages of using it.