I don't think the clunk is due to lack of tighten, because i didn't made a lot of effort on tightening it on my car.
The parts of the mount were all in good shape, nothing inducing excessive wear or something like it.
Are your driveshafts all ok?
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What is a hybrid?Honda engine...Ford brakes...Peugeot chassis...Vauxhall steering...

306 Rxs
i couldnt get any more purchase with a spanner so ill whip it in work one day with an 18mm deep and torque it to about 70lbft and see if that helps!