For those who have a tow bar wondering if that also gives some reduced body roll on these cars ? Following video depicts the installation of the CURT 13143 class 3 hitch on a 2010 Lexus RX350; reinstallation of F-Sport support bar over the tow bar seems a bit of overkill;

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The F-Sport has a $600 dollar damper connected to the frame. The tow hitch does pretty much the same thing. The Curt hitch has an additional bracket for those who have the F-Sport so they don't lose that suspension piece but to be honest you don't need it with the hitch. So to answer your question yes the hitch stiffens the rear substantially

 

For the Lexus factory tow hitch, the installation instructions say to remove the damper stabilizer bar. I don't know if it could be reinstalled since the instructions also say to remove the original tow hooks. When I installed on our 2013 RX350, I had to remove the bumper cover to access the factory wiring to connect the trailer light harness but it was a straightforward install.