At 35 m/s speed of the shaft kinetic energies for slider collision to the step end:
- 7 mm; for slider 1.8 J, for water 3.11 J
- 8 mm: for slider 1.16 J, for water 2.23 J.
I would say this titanium hydro-damper sliders would work. The problem might be because the wall of the 8 mm slider is maybe too thin, 0.42 mm..and there is very small gap between the tail step and the slider wall, only 0,08 mm. Maybe the bore would be better to be 8.05 mm to reduce the tilt of the slider and the rear step could be shorter, maybe 7 mm? Very important is that the shaft tail cone must be in a very center of the shaft! The slider must not touching the shaft tail step end during moving along the shaft in any position (sideway).