I did some digging and indeed found their location, but thank you very much for the conformation!
Also found out that currently is indeed the best time for them, almost 4 times as much chance as most other months. It would have been nice to be able to combine it with a trip to Apenheul, but that's not happening soon.
Maybe when i find something else to combine i will see them this year, and otherwise, they will be there next year again : D
I saw at least 50 on a 10-minute walk through the creek yesterday, if you go behind the mill (not private property) you'll find a large log over the water where you can get down to the creek. Walk under the log and follow the water upstream (the creek splits, follow the one that doesn't go back to the mill) up the little waterfalls. That's where I found most of them. But you'll also find two or three if you do downstream a bit
