Depth of M3 screws on 37D gearmotors?

I seem to recall reading about a maximum suitable depth for the M3 mounting holes for the 37D gearmotors, and exceeding this depth would hit the gears or otherwise get in the way of the movement.
Reading through the specifications on the catalog page now, I can’t find that notice.
Is there a minimum/maximum “safe” depth for the M3 mounting holes of the 37D gearmotor gearboxes?

Hello.

We recommend that the mounting screws not go more than 3.5mm into the mounting holes on the face of the 37D gearboxes.

Grant

Thank you.