Knocking Hardrace rear trailing arms

[JB21]

Getting knocking from both Hardrace rear trailing arms. Bolts are tight but when I get someone to rock the car back and fourth its seems theres space between the bolts causing knocking. Are you supposed to use bigger bolts when fitting these arms?

Another thought, as I didn't fit them maybe the length  could have been set wrong when installing them?

[Rich.B]

I also get a knocking noise from my hardrace rear arms. I've also fitted some large square washers on the subframe end to act as a lock out kit, I didn't notice the bolts being smaller but I'll give that a check.

 I just assumed the added noise was down to the pillowball style joints instead of bushes. If you managed to sort it then be sure to post the solution👍