This works much better, I got rid off the XMP. And all the Exif seems copied.
But looking closer, the content has changed not the outcome.
'Shutter speed value' was '-118/32' which is 13 seconds is changed to '-11791/3196' this is also 13 seconds.
Maybe I have to explain what I was trying: I have a huge pile of photo's. I'am not interested in the actual photo's. So I thought of saving disk space, if I could minimize the picture without changing any EXIF data.
Is this possible?