To second Erwin: Yes, „Hull Down“ command is pretty vague. IIRC, when given a hull down command, the AI moves the vehicle along the ordered path and settles at the first hull down position. Regardless in which direction. I.e., you may want to search for a position straight ahead, but if the first available hull down condition is perpendicular on the right hand side, your vehicle stops in that position and turns right.
I personally, indeed, do rather check the line of sight in the direction I want to move, move the tank to a point just before the line of sight „breaking point“ and then inch a little forward with a hunt command.