Has anyone else noticed any vibration in the gas tank at about 4-5K  just wondering, :dunno:  also, how much time and what kind of pita would it be to paint the engine? any feedback would greatly appreciated before I start a project I might regret!    

Vibes at ~ 5k,  Yup.  I think just about everyones got 'em.  It has something to do with the reasonant frequency of the tank/frame, (which is why its only in that rpm window and not everywhere)

It's when the GS begins to hamonize and become one with the universe.

It's normal.