Towbars now have to be EC Type Approved. 'Witter' tow bars usually are, but best to have a foldaway towbar correctly and legally fitted by the Honda dealer. Non-folding towbars are antisocial because they cause considerable damage to other cars when parking. You also need to check what further changes need to be made. The car may need higher capacity engine cooling fans and, if the car is automatic, the transmission may require an extra oil cooler