Sometimes there is some " backlash" in the bolts bolting the tow bar assembly to the chassis of the vehicle, I needed to go as high as possible with my tow bar, when the twin axle boat trailer was un laden, the rear wheels didn't touch the road with a 4 bolt Ford (Brink) bar, so I bought a much lighter built EU approved Witter, that with lifting the bar and tightening the bolts, met my requirements. All legal of course.
When I spoke to "Brink" in Holland, they said, no modifications, no raiser plates, I couldn't even enlarge the two top holes and fit a bog standard two bolt ball, that may have done it... What a game.
Why bother? well if you have a crash, whilst towing, then the insurance companies know of this issue, and will use any excuse not to pay out, then you are not insured, then the police will have a talk too.
Note... I still have this super strong Brink tow bar with 4 hole ball, waxoyled from new, but only on the vehicle for a year I guess, stored in the shed. Only suitable for Pre "S" registrations as not EU approved, mind you, might be legal for all in two years time lol....
Anyone interested? Location Cannock /Lichfield area.