Hi Maarten,
The net cutter on Type IIs had different configuartions which you can see below -
The style numbers are numbers I have assigned and are not in any way official. They are not chronological either. Note the drawings above are just intended to show the changes and are not accurate in regard to the features. For example, there was a bend in the rearmost bar that is not shown above
The U-bootwaffe changed their minds on whether they were required a few times. We know that they were fitted in the early war years but after March 1941 they were removed. The pre-war photos tend not to have dates on them and that makes it hard to determine when they were present and when they were fitted during the pre-war years. It does look like boats had them at the start of 1939, that they were removed early in 1939, and then refitted around the summer of 1939 or so. I've also seen boats during the Spanish Civil War without the net cutter so this provides a time period when they were absent (at least on some boats).
Do you know when you are depicting your boat and which boat you want?
If you send me a PM with your email address I can send some photos.
Cheers,
Dougie