603.961 Valve Stem Seals - When are they pressed on completely

[wgilmore]

Hi:
I am replacing the valve stem seals on my 300SDL but am unsure when the seals are seated correctly.
I've read Dave's posts regarding 603.9 valve stem seals needing to be pressed on until they are all the way down and hard to pull off.
The process I am using is to press the seals on by hand and then place a washer on top of the valve stem seal. On top the washer I place a deep socket
and using pretty good force by hand , pressed the seal down as far as I can.
I don't know if this is fully seated , don't want to push them on to the point where they are damaged or are seated to far down the stem (if that's possible).
Any feedback would be greatly appreciated. Thanks.