It says in the manual that the ST220 is not homologated to tow, there is no towing weight specified on the VIN plate for ST220's.

You can tow perfectly legally and in confidence with an ST TDCi, the same can be said for the 3.0 V6 204ps which uses the same size 240mm clutch as the ST220.

The exhaust does not get in the way of the tow bar, the two back boxes are no-where near the mounting plate.

Oh and listen to this!

http://youtube.com/watch?v=Pu7kgDjJXno