Makes sense! Thank you very much. Yes, I can see now how that spot is the cleanest spot to install. Very nice install.
Do you recall if the part is threaded or smooth?
I went to Webasto's accessory catalog and will continue to look for that part, but can't find it yet.
https://www.webasto.com/fileadmin/webasto_files/documents/international/hd/catalogues/heavy-duty-heating-accessories-catalog.pdf
There is a part (order number 1322827A) that is similar (not a solid stub piece like yours), but a right angle steel piece that says is made for plastic or metal tanks. (pdf page 7, manual page 13 bottom right). It doesn't have the large stub look that you have (which seems more stable and less likely to "move" or "twist"). I can try to call them to see if they still sell the part you have.
Again, many thanks. You have no idea how much I appreciate your response.