I have Koni's on my 71, along with progressive springs, My settings are 3 in the front. This gave the car good turn in, helped with brake dive, and gave a firm but not jarring ride. The car seemed to like the rear being softer, so I set it at 2.
I did try the higher settings, 5 on the front and 3 on the rear. This might be good for autocross or a track day, but on the street you'll feel every crack in the road, and the rear end dances a bit over bumps.
Mike Halleck
Chesterfield Mi
71 280SL
68 250SL (parts car)
94 E320 Coupe