It's an odd screw depth for me when I try to use a hex socket ended type of screw to make it nice and flush on the underside. Found out that a 9mm screw actually works best for the application (at least for me). I had to go look and find them and ended up ordering them from Aliexpress. 8 was too short and 10 was to long as mentioned.
Love the print though. This was the only issue I ran into.