I finally had a chance to install the arms last night. The arms fitment is great. The clunking noise is all gone now. The rear suspension feels stiffer which is nice. My car is noise free for now. I am very happy.
Thanks to delubozparts' quality product and CJ_Boxster's helpful instuction.
Just like CJ said, REMEMBER to tighten the nut on the adjustible neck. I forgot to tighten them so they were rattling bad.
I am a happy man.