I had my Witter / Westfalia tow bar fitted this week. While the cut may be invisible viewed from behind it is fairly substantial when viewed from underneath!
There should be no need to remove any kitchen panels as the wiring instructions specifically say that the wiring goes underneath the van and comes up beneath the passenger seat. I've no idea if this is unique to the vehicle dedicated wiring that I chose.
I had a Westfalia removable towbar fitted on Monday by a local specialist. They ordered the vehicle specific wiring kit, but weren’t sure if the V Class was TP (trailer prepared) or not - Mercedes and BMW were in their experience generally TP. However, it turns out the Marco Polo isn’t TP. Fortunately they bought in both the TP and non-TP wiring kits. I’m not sure where the wiring went, but I had assumed it would be slung underneath in a proper loom.
Regarding the ‘invisible’ bumper cut, it’s not entirely true. Whilst the vast majority of the cut is under the bumper and unseen unless you crawl on your hands and knees, you can see where the lip on the rear underside edge of the bumper has been removed. When the towbar is fitted it is hardly noticeable, but when removed you can just make out the electric socket and missing bumper lip.
Not a big deal I suppose - I’ve had a lot worse over the years. But I wish the manufacturers of van type vehicles would design- in the provision of towbars at an early stage because, presumably, such vehicles are far more likely to tow things than the average car.