<html> Dear All- This thread is extraordinary for the range of issues it contains, and it would be a shame if it dissipates before, at least some of these issues crystallize  (didn't want to go so far as to say resolve).  There is undoubtedly some overlap in the following. The Issues How do the 'Lines of Force' differ in an openface block; bushing-less covered block; covered block with bushings? Do the 'lines of force' of a bushing-less block change if, over time, the pins, en masse,  begin to contact plate?   Would such an occurrence necessarily be due to poor flange fit, or could either poor top fit or soft wood be factors? How much pressure against what resilience factor (durometer?) would be required to have an impact  on these "lines of force'?  At what point does 'support' begin to alter function? Would you assume that a new or newly rebuilt instrument without bushings in which tuning pins already contacting plate is starting out with an acceptable alteration in its design parameters?  What is the intended design purpose of plate bushings? Which are unintended side effects? - Dust and beer repellant - Centering of drilling for tuning pin - Support against flagpolling / springing - Alteration of 'lines of force' - Contribute additional torque to rotation of pin How would intended purpose dictate material employed (soft wood, hard wood, delignit, plate contact) ? How do tuning pin bushings contribute or detract from TUNABILITY, as opposed to tuning STABILITY? To what degree (if any) is the springing / flagpolling tendency a valuable tuning tool? How does the density of the pinblock material used with a bushing-less plate affect the ability to use springing effectively? What is physically taking place in 'springing'?  What is happening to pin, along how much of its length?  to the top of the tuning pin hole or the bushing? What part do characteristics of the tuning pin play in tuning characteristics? <x-tab>        </x-tab>a) Tolerance to nominal size <x-tab>        </x-tab>b) Type of steel <x-tab>        </x-tab>c) Method of thread formation <x-tab>        </x-tab>d) Finish (blue, nickle, etc) Do small and large ply blocks have different tactile tuning characteristics if measured at the same static torque? Relationship of pin maneuverability to friction ratio of front string bearing points as a determinant of tunability.  What is too little friction? too much? Please remember that you will be marked "incorrect' for any questions unanswered.  David Skolnik </html>