I have done a few times at Quicksave without problems, but then my wheels, tyres and car are different. You seems to be running around paying for the balancing. Why not stay with say Lim Tayar as you have already paid them so they have to rectify the vibration.
Yes, if the car body vibrates as high speed, probably is the rear wheels out of balance.
Yes, if the car body vibrates as high speed, probably is the rear wheels out of balance.