Grumpy_Mike:
No.Like this:-
The square boxes are the servos.
yes, that was kind of my original point about having to "insert" the Pi circuit and not being able to (be lazy and) "just plug in the servo connection" 
Grumpy_Mike:
Your right it wasn't so that suggests you don't need that much inductance so you only need a small value. That was a general purpose comment for heavy motors.
i see - okay then, i'll try and hand make a coil just to see if it holds back the jitter.
(more to do with "see what happens" than designing the circuit ideally.)
by my calculation, a simple straight (air core) coil of 20mm radius, 10mm long with 20 turns should give about 63 micro-H. (that's already 2.5 meters of the enamel wire needed(!), i don't have any ferrite (nor iron) core - now i get the "don't bother making your own" comment !)
Grumpy_Mike:
You can't say without first defining the period of the pulse and you don't know that.
...
the effective resistance an inductor presents when fed with an AC signal. This is a pure inductance where the actual resistance is considered zero.
so, good'ol V=IR applies here where the (supressing) "resistance" required would be an equivalent of (6V / 100mA) = 60 Ohm ?
and if i can get the frequency; the (minimum) inductance would be L = 60 / (2*Pi * f)
would the inverse of the pulse(time) be considered the 'frequency' ?
(am just realizing that AC doesn't have to be a constant period, and that a "DC spike" is also AC !)