The last trial tonight was 40ml Rollei RPN plus 260ml water. All other parameters were left untouched. I agitate like this: 1 inversion every 15 seconds (except the bleach where I use 1 inversion every 5 seconds). The aim is 12 minutes in the first developer. With this configuration the frame exposed at 200 iso is just perfect.
To get the frame exposed at 100 iso perfect too I guess I've to diluite more or less minutes.