Vibration at 55km/h exactly under acceleration

[nzoliver]

Howdy!
Should there be an angle difference between the rear diff flange and the 3 spoke flange on the end of the drive shaft (causing the rotflex to be compressed at the 'top' and stretched at the 'bottom'? There isnt a huge difference but there is a difference and i'm picking the spigot inside the shaft will be causing the shaft to 'swing' a little as it sits further up the shaft than the 'centre' of the 'flex' joint. Would I be correct in assuming this could cause a vibration?