Hi Linda - not entirely sure what you mean by 'vertically detachable towball' but do you mean like the attached image? This is like a big (and heavy) letter 'U' with the part that slots into the tow bar underneath the rear sill. Mine is like this on the VW Touran although whether or not it's Westfalia or not I couldn't really say. Good chance it is though as it's VW's own and I had the entire rig - tow bar, ball and electrics fitted by my local dealer. It's simplicity itself to fit although you do need to get down on your knees and it's quite a heavy lump of metal.
As to whether or not it's a good choice - well that's a difficult one to answer requiring a horses for courses type answer. I went with the dealer option because they made a right hash of a collision repair and as I was in the market for a tow bar etc the dealer offered me the entire rig free by way of compensation. That said, even if I'd had to pay for it myself I'd still probably have gone for the dealer option.
towball.jpg - Bild entfernt (keine Rechte)