I have used dxf imports before in Layout 15.7 and we had a simple way to use layers for the basic designs and then import a v12 dxf.
But when I try to develop a basic board outline for Allegro 16.3 or 16.5, there does not appear to be a way of importing the plated and non-plated holes into a PCB. What is the class and subclass for the hole imformation?
Drill chart?? No way... You need a Padstack with a drill to make a hole in the board - or a Keepout / Ouline and so on. The DXF is going to give you the location for the hole, then you need to snap the mechanical part to it. The "best" way is to layer the DXF data so that the Outline is on one DXF layer and the "hole targets" on another. The outline might not be closed so import it to a temporary layer like Board Geometry Assembly Detail, the use Shape>Compose Shape to close the shape to the required Board Geometry Outline layer. For the Mounting holes, Place Manually, set the "Library" option in Advanced Settings, select Mechanical Symbols from the drop-down in Placement List, select the Mechanical Symbol in the list, "Hide" the form and the hole will be on the cursor, locate and hover over the target location and use the right-click>Snap To menu to snap to the location. The holes will show up in the Drill Legend when it gets created.