Yeah it is a bit weighty,I think about the 4kg mark too.
I bolted it into the inner chasis of the car,I used 3 bolts on each side.I tightened it as much as I possibly could.It's solid as.I notice it the most say when U go off or onto a driveway,the normal twisting feeling and sometimes creaking sound is gone.It's real firm now.

Thank U and thank U for telling me it would fit before.U we're right!