Have the Db1290, I am not off on the moisture content left after an air cooler, though 70% makes it possible to paint a car without having drops of water interfere with the paint job. In NYC, in the summer my coalesence filters just after the coolers would have a constant flow at 95°. On my first 5hp compressor I also had an intercooler (Db1260), cooler between the first and second stage, it also dropped out water, and made the air denser, going into the second stage.
"After a weeks use in summertime Atlanta we might get an ounce or two out of the tank."
There was still moisture in the tank, unless the temperature was brought down below freezing.
"I don't understand why an aftercooler isn't a factory option on the cheaper 5hp 175 PSI compressors."
Because the bean counters at the manufacturers would be having heart attacks.
"so I am going with 24+ ft of 3/4 tubing after the tank instead."
There will still be considerable moisture in the output after 24 feet of 3/4" tubing. Copper is a good conductor of heat but a poor radiator of heat, especially bright copper; also 3/4" does not provide a large surface area. The swirl coils within the Hayden coolers make up for the limited surface area of the copper tubing. After years of oxidation, when the copper becomes darker, it radiation output improves. Black copper, either chemically darkened, anodized or painted is a better radiator.