Thanks for the links @Mark - really interesting - especially the second item.  I usually end up actually going all the way to the fingerboard (although my finger-pressure is pretty light - I mean I'm not actually "stabbing into the strings"), but sometimes I will do as he suggests - and when it works for me (LOL) I get a nice tone from the instrument.  I suspect the quality of the sound (and the actual ability to do it) probably depends to a fair extent on the strings and indeed the instrument itself.