Ohio,
The link you provided didn’t work for me. Here are a few relevant paragraphs from The Common Cents System (CCS) by W. Wm. "Dr. Bill" Hanneman that you mentioned:
“We recognize that in fly fishing, it is the line which is cast, and that it is the momentum of the line which pulls the fly along behind. Since momentum is equal to the product of speed x mass, the speed of the cast is very significant.
Actually less than 10% of the rod loading is due to the weight of the line, over 90% is due to the speed of the cast. This is the reason any rod can cast any line - the caster merely adjusts his speed.
However, fly-casting is most pleasurable if the weight of the line is matched to the power of the rod, and in the case of fly lines, weight varies with length. The CCS articles provide charts relating the number of common cents to ERN, WL, and the distance one wishes to cast.
Of course, if your casting style is so ingrained and/or productive of that nebulous right feel that you can't or won't adjust your speed to optimize your equipment, adjustments to the CCS recommendations are necessary. If you know your casting speed is greater than average, try using a size lower line - if slower, try a size heavier. Remember, you are only creating momentum.”
Rod weight is measured with the 1st 30’ of line. If you most often cast 20-40’ or less going up a line weight might work better for you. Don’t forget, with a 40’cast you only cast 20-25’ of fly line because you must add the length of the rod and leader.
I you need to bang out 50, 60 or 70’ casts on big water, going down a line weight make work better. Think of this, rather than getting a new rod, you can underline it when fishing big water and making long casts. Use the recommended line in medium and smaller streams, and over line when fishing in tight quarters and making short casts. There are however other factors to take into consideration – rod length, casting with weight or weighted flies, wind, etc.
WARNING: Don’t let you wife read this. It may blow your cover on why you tell her you need all those different rods.
Most of the time I prefer a faster rod because I can adjust the speed of the line (which creates the power) depending on how far I’m casting, and if a tight loop is needed to execute the cast because of conditions (wind, casting through/around obstructions, etc.). With a slow rod you have less control over the speed and power of the cast.
Don’t be afraid to play with different line weights on your rod. I wouldn’t try going more than 1 wt + or - though. Try casting on the lawn with different line weights to see how it works for you. Good luck.
