A couple of thoughts from alot of cycling years. I started riding as an adult in 1973. I was oh,so impressed with the latest Campy parts and bought my stuff piece meal, because of price. I have never had a problem with adjusting any quality brake. I always used the speciel seratted Campy washers and clamped down firm. Then made final adjustment with a small hammer and brass punch.
I used Campy brakes till a couple of years ago, and then discovered Mafac Competitions with Cool Stops.
No way is the SP in the same class of power.
I also use Dia Compe straddle cables ( shorter then Mafac ) after reaming the end holes out on the arms. The shorter the straddle, the quicker the pull starts.
You'll notice on the front cable hanger stop, there is some daylight between the hanger and the headset adjusting cup. As you squeeze your brakes the hanger pulls back towards the bike. Usually an extra washer behind the stop nut will press against the top cup, removing the flex.
If you have a friend with a small milling machine, buy some small brass stock from your local hardware store, and give him a set of the teflon brake arm washers and bushings from your Shimano, dia Compe, or Weinmann brakes and ask him to make you a set out of the brass.
The Competitions already have the brass bushings all they need are the washers.
I'm in the process now of brazing on the Mafac mounts to my stays.
As the small amounts of flex here and there are removed, you pick up power, speed of modulating, and quiet. Then you also have the extra clearance for mud or fenders.
This sounds like a lot of work, and it is. But, I'm retired and have my own metal machinery, so for me, it's just another project.