This small document should give you a rough idea of what kind of values you should use for the physics settings of some of the VP elements. All values are just recommendations!
The "Scatter Angle" (basically the 'randomness' of physics interactions) is used in calculations together with the "Global Difficulty Level", so to have a better global control
for all elements, set the "Scatter Angle" of elements to 5 and limit the behavior/impact of the "Global Difficulty Level" by setting it to 10-20% or higher to control the overall gameplay difficulty.

Playfield:
----------
Gravity Constant   : 0.97 - 1.0
Playfield Friction : 0.075+       (This depends on how fast the ball should roll on the playfield. 
                                   EM tables are usually slower than modern tables. So for slower ball movements raise this value and/or modify the table slope)
Playfield Elasticity: 0.25


Flipper:
--------
Mass               : 1.0
Strength           : 1200-1800 (for EM tables) 2200-2800(for modern tables)
Elasticity         : 0.8
Elasticity Falloff : 0.43
Friction           : 0.5 or 0.6
Return Strength    : 0.058
Coil Up Ramp       : 2.4 - 3.5

Rubbers (default):
------------------
Elasticity         : 0.8
Elasticity Falloff : 0.4
Friction           : 0.5 - 0.6
Scatter Angle      : 5

Rubber for posts (the yellow or black kind):
--------------------------------------------
Elasticity         : 0.65 - 0.75
Friction           : 0.65
Scatter Angle      : 5

Walls as metal side walls:
--------------------------
Elasticity         : 0.3
Friction           : 0.15 - 0.3
Scatter Angle      : 5

Walls as metal wire/guides:
---------------------------
Elasticity         : 0.375 - 0.5
Friction           : 0.1 - 0.2
Scatter Angle      : 5

Walls as wood walls:
--------------------
Elasticity         : 0.375 - 0.425
Friction           : 0.2 - 0.3
Scatter Angle      : 5

Plastic drop targets:
---------------------
Elasticity         : 0.35 - 0.4
Friction           : 0.15
Scatter Angle      : 5

Stand-up metal targets:
-----------------------
Elasticity         : 0.3 - 0.35
Friction           : 0.15 - 0.25
Scatter Angle      : 5



jawdax' take on suggested values:

Gravity Constant   : 0.8 - 0.83
Playfield Friction : 0.02+

Playfield Elasticity: 0.25


Rubbers (default):
------------------
Elasticity         : 0.6
Elasticity Falloff : 0.2
Friction           : 0.5 - 0.6
Scatter Angle      : 5

Flipper:
--------
Mass               : 1.0
Strength           : 1200-1800 (for EM tables) 2200-2800(for modern tables)
Elasticity         : 0.55
Elasticity Falloff : 0.1
Friction           : 0.1 or 0.2
Return Strength    : 0.058+
Coil Up Ramp       : 2.4 - 3.5
