Resonance in torsion bar from torsional forces

[CHagen]

Ive got a debate going over an idea i had about the possibility of torsional resonance or oscillations with in a tosion spring. The current use of the torsion spring is about 20" long and .5" diameter with a .035" wall thickness. At each end is an leverage arm that recieves an input of often varying displacments and velocities or amplitudes and frequencies if you would rather consider it that way.

My idea would use a 60" long bar with .75" diameter and the same .035" wall thickness. I have been able to quantify some of the benefits to the system but thats beside the point.

The argument against it is that the longer bar will create more oscillations and "chatter" of forces between lever arms on either side due to a longer torsion bar having a tendency to oscillate within itself more so than a shorter bar. Notice im not talking about oscillations of the system the bar interacts with, since that is related to K of the bar. Im talking about the bar torsionally vibrating along itself between the lever arms....

I felt that this would be more related to stiffness between leverage arms as well which is a function of length, diameter, wall thickness and modulus rather than just length alone.

Can anyone comment?