Would this work? Drill and tap for a small socket head cap screw, just inside where a spot face for the nut would land, so that the flat of the bolt will be tangent to the SHCS. I'll try and find a picture of what I mean. I found this trick in this invaluable book https://www.amazon.com/Fasteners-Plumbing-Handbook-Motorbooks-Workshop/dp/0879384069I still would like to come up with a way of locking the nut.
I have made a mental note before that you have done this, but it is nice to see it in pictures. Thanks for posting that!The VW bottom oil plate is made from heavy steel. I made a plate from aluminum to save weight and added a small sump so when doing a hard slip It will not un-port the oil pickup tube. <snip>