Or: What kind of Idiot has designed that engine?

I had the good idea to install an oil temperature sender into the oil pan.
At the next oil change I drained the oil and measured the thread of the oil pan screw.
It's 16.5mm or 0.649"
I have a metric and Witworth and SAE thread lead/pitch gauge. None of them fits!

So what the heck kind of thread is this? I came to the conclusion it doesn't may be good anyways to install the sensor in the oil pan were it is vulnerable to rocks and obstacles.

So I wrote VM Motori in Italy an E-mail where to place that sensor.
They responed with a single sentence: Mount it into the oil gallery.
No word of a thread size-nothing at all.

So I crawled below the engine to have a look at the oil galley.
Needless to say that the exhaust manifold, the intake manifold, the EGR, the Turbocharger, the engine mount, the oil/watercooler and the oilfilter mount is in the way to prevent access to the screws at the main oil gallery. I have to disassemble the complete engine to gain access...for a single sensor

What do you think about those dipstick sensors? Any experiences?