1) Will the vibration occur at rest w/the trans in neutral & the RPM's in the offending range?
There is no vibration in neutral at any RPM range.
2) Generally a bent driveshaft won't unbend itself or stop vibrating popping the trans out of & back into gear, nor simply loading it.
When I had my shaft balanced, they told me that it balanced out perfect.
3) If You grab the installed prop-shaft at the front, how much can You move it up & down?
There is some play in it. I can't recall how much, but I was able to move it.
