I made a few more tests using 470pF for C2 and 470pF for C5.
Oscilloscope: DC coupling, probe x10, scope setting x10.
The measurement point for the oscilloscope was on the output of the power supply.
R23 was always 100R/3W.
1. Rdrain=10R, Vout=25.5V, SlowCC=3.25A
DS0567-DS0571.jpg
2. Rdrain=1R, Vout=25.5V, SlowCC=3.25A
DS0572.BMP
3. Rdrain=10R, Vout=25.5V, SlowCC=1.63A
DS0573-0574.jpg
4. Rdrain=10R, Vout=12.1V, SlowCC=3.25A
DS0575-0578.jpg
5. Rdrain=1R, Vout=12.1V, SlowCC=3.25A
DS0579-0580.jpg
6. Rdrain=10R, Vout=12.1V, SlowCC=1.59A
DS0581-0588.jpg
7. Rdrain=1R, Vout=2.49V, SlowCC=3.25A
DS0589-0594.jpg
8. Rdrain=1R, Vout=2.49V, SlowCC=1.66A
DS0594-0598.jpg