I reread the chapter in Aquatic Systems Engineering, I'm not sure it applies to a drip system, but its gist is reared toward a closed loop system of filtration, not the continuous addition of new water.
On the other hand I do see the point that simply dividing the total gallons by water replaced is not a realistic look at the amount of water being changed.
This is why I always tried to do a 30% water change on my system every other day. in theory, a 110% water change per week, although more realistically much less.
My barometer was the drop in tanks alkalinity. When I changed less than 30% every other day I would notice a 20% or higher drop in alkalinity almost immediately after a water change, which suggested that fish urine was almost instantaneously eating up 20% of the value of the water change (20% of the new waters buffering capacity). But doing a 30% change, about 10% (sometimes less) of the new waters alkalinity was neutralized, a value which I considered tolerable. I know most people use nitrates as a barometer of water quality, but I found the quick reaction of alkalinity to be much more "real time" test of my tanks actual water quality.
I'm not trying to lessen the significance of nitrate, but I had access to an alkalinity titration set up, along with the other testing parameter tests, which most aquarists probably don't.
As to baffles, I found them to be a hindrance to performing maintenance, so discontinued their use early in my sump experimentation process.
I found hanging filter bags for mechanical on the sump entrance end, and placing bio media in mesh bags mid sump, was just as effective as crowding a tank with baffles that got in the way when doing work, or worse were a hassle to remove when I decided things needed to be altered.
