In general, the DOF is split 50-50 from where you focus. Since you want both the front and back edges in focus, you need to set the focus point about half way into the model (as a starting point for testing). A line on the top of the model would help you in that point.
Since you are using a tripod, the slowness of the shutter speed should not matter, so there should be no real need to increase the ISO thus reducing any digital noise.
---------+---------+---------+---------+ Joseph K Seattle, WA, USA