Take a look a "Benbo" Tripod It will reach over your bench easily and has a ball head. They are incredibley? versatile.
Mount your subject on the rail, this way the camera remains stationary and rock solid and the subject is easily moved on your rails, also rock solid.
With the rails laid (unfixed) on top of your bench there will be no bearing noise and your subject will appear to move smoothly in both planes and remain in focus. Placing a board? over the rails will hide them successfully, and give the illusion the camera is moving. I think you will be very pleased with the resulting images. You could also mount a turntable on top of the rails then you will have left and right; back and forward and the ability to revolve smoothly too.
(anyone got a record deck?)
You may be able to adapt your current tripod to a configuration similar to the Benbo.
This would be a lot easier to achieve and you already have all the bits needed. Hope this helps.
Great you tube channel and forum by the way...keep up the good work.
(I,ve even started saying "Tah Darrr" again
)