The other day when I was out fishing in the driftless, my casts (when I was doing proper casts) were topping out at about 15'-20' (many were even shorter), I just didn't need to reach out any farther than that. At those distances my 4wt wasn't really loading properly, not that it really mattered that much I suppose. But I was thinking it might help to upline at those distance so the rod loads with more less line out and I can then make a more conventional casting stroke. Does anybody else do that on small streams, or am I just making excuses to buy a lighter rod that I can upline (I mean, I do have 5wt spooled on one of my reels, but that wouldn't be any fun).
Instead of buying new line and up lining, why not invest in a casting lesson instead? I am predominately self taught but have the benefit of having a great friend who is a much better caster than I am. I learn from him all the time on the river. I took a casting lesson a couple of years ago and I can't tell you how much it improved my casting. I'm far from a master caster but it was very helpful.
Are you dry fly fishing? Then cast downstream to the fish. They won't be effected by the heavier line.
I don't understand your objection, "I do have 5wt spooled on one of my reels, but that wouldn't be any fun." Apparently casting the 4 wt line on your 4 wt rod is not fun or else you wouldn't be asking the question about up-lining. It can't be about fighting the fish since you still would be using the 4 wt rod.
I routinely used 6-wt line on a 5-6wt 7'3" fiberglass rod for the driftless. Perfect for heavy scuds and dealing with wind. I really wouldn't want to go any lighter than a 4-wt with a lead-back scud pattern.
Some sound advise here already. I dislike over-lining as it dulls tip reflexes; so important in precise presentation. Your #4 should be able to execute short casts if it is properly matched with its line as MP indicates. That may well require trying several different 4-weight lines with it. Further, casting lessons or coaching are a great idea for all of us no matter how experienced. Fly fishers are among the only stroke sport practitioners who routinely eschew working with a pro. Tennis players, golfers even professional baseball players practice but we just go fishing. And, it shows.
When I am casting short distances, I do upline--either by using a RIO Grand or a SA GPX, which are actually a half line size heavier than their stated weight. If I am going to be nymphing at short distances, I will upline by a full line size.
The stated line size is based on the weight of the first 30 feet of line. If you are casting 15 feet, you will not have enough line to fully load the rod.
My worst 'sin' in form is my thumb. I have a tendency to let it drift to the left of the grip a bit. When I do that, my presentation goes all to heck. No kidding. Just that little big of flaw ruins my cast. I can 'get back in form' with thumb pointing down the rod and you wouldn't believe,,heck I don't believe,,,how much better my presentation is,,and esp at SHORT RANGES.
Now, you say that may be mental. It may indeed,,but I do not think so. In any event, that is how it is. I move my thumb , my cast suffers bad. Pay attention to areas were you might be breaking form and not even realize it. I fully believe that you have to have good mechanics for a good rod to do what that rod was designed to do. They compliment each other.
I have a question, what rod and how long? I use either an old fiber glass Full Flex or a bamboo flea for small streams. The bamboo is a 3 weight and works just right and the fiber glass will take any line from a 4 - 7 but I like a #5 line.
With todays fast action rods I can see how short casts on small creeks could be difficult if you are using an 8.5' or 9' rod. If you fish small creeks a lot maybe a 6'6' slow action rod is in your future. Not much need to ponder line weights with slow rods. Just say'en,
The rod that I'm using most is my Loomis GL2 7'6" 4wt, I also have a Redington CT 9' 4wt. Neither are particularly fast rods. I wouldn't exactly say that I've been having a hard time, it's just that by the time I'm carrying enough line in the air to feel the rod load, I'm going to overshoot the water. This is particularly a problem when I'm fishing from the bank, getting up over the weeds and essentially casting down 10-15' to the opposite bank, and doing short little drifts through holes or past undercuts... I can do it, but I'm not getting the feedback from my rod that I'd like.
It's not as much of a problem when I'm wading when I can roll cast and longer casts are more practical. But on those silty bottomed streams I tend to stay on the bank if I can because I'd prefer not to drag my size 14s through the silt and disturb it... I also feel like I catch more fish this way because I'm not fouling the water (especially when working down stream).
As far as overlining my current rods with the 5wt, I only said that it wouldn't be much fun because it would mean I wouldn't get to buy new toys.
And, yes, I could definitely use some casting lessons.