You will also want to use a very thin 0.005" (0.15mm) motor shim between the e-clip and the piston to take out the enfloat. The piston is just a tiny bit thinner than the HPI one and you will end up with a small deadspot if you dont use a shim.....you will see what I mean!
Once you have done that they will be silky smooth. The pistons really do make a difference in these dampers. Beautiful and easy to build.
We used the 3 hole pistons most of the time here in the UK.
Hope that helps