So if the passenger happened to weight 250 pounds, you'd have to turn the adjuster on each spring 10 turns? And then crank it back up 10 turns per side when the passenger rides with you next time? Hmmmm. Kind of makes one understand why some people just stick with the air shocks.
I seem to remember a better idea from Works Performance. Two springs per shock, set the main preload with the main spring and then adjust for a passenger with a simple lever for the secondary spring. 
Jerry
Well my 09 SERG had the air shocks which sucked, and changed them to progressive. Huge improvement. My 12 SERG came with HD premium low, about the same as the progressive 944 I had on the 09. My 13 SERK has the same Hd Premium low, pretty good.
Got my 15 SERGU, first thing I noticed was the rear felt loose in a hard curve, and the ride sucked. Played with them for three weeks. Still felt loose and wallowed like a fat pig in the hard curves.
Put the Ohlin HD 159's on it. Rides better than any harley I have ever owned. Feels very planted in hard fast curves, never feels loose. Ride is very good. Also very simple to change from firm for the twisties to more supple for the interstate.
As for changing the sag, its easy just takes a few minutes. However for me, its usually only one turn for when I load my gear for a trip. I do not even have passenger pegs or boards on my Ultra.
I am seriously thinking of getting a second set of Ohlins for my CVO King