There are a few designs of tow bars in existence:
This one seems to be a strong construction, being fixed with the existing
rear bumper brackets and under the floor boot. The fitting instruction tells,
that the towing bracket may be used with or without the extension plate, thus
giving two towing heights i.e. 11 1/4'' and 14 1/4'' approx. unladen.
The next one is of a different design. The side arms are fixed as on the
above model, but the upper crossbar (B) is fixed on the bumper bolts. The
fitting instruction tells that a minimum amount of the overriders has to be cut
to clear to fit this.
Another disadvantage is the number plate. They wrote." Re-fit number plate
assembly either at an angle beneath the lamp with 2 screws through holes drilled
in the centre bumper rail, or fixed to the boot lid above the lock, illuminated
by removing small panels and reversing the lamp assembly."
I do not have any further information about the next one. If you look
carefully at this bad quality photo, you see the bar under the bumper and only
one bracket (instead of two on the first model) coming from under the rear boot
floor.
