As I was waiting today for someone to visit me in my shop, I took the chance and finally drilled and tapped the cases in M10x1.0 for a standard VW 0.9Bar opener oil-pressure switch. Nothing fancy really, just make sure you drill straight into the case. Other than that...
With a drill guide
Drilled it out to 9mm.
Tapped it and installed the sender.
Next step will be to take off the engine covers, remove the rotor and the cylinders/heads and then get into the meat of it and make some decent progress (finally).