kdee122,
To model a hexagonal cut-out, you must create two hexagons diagonally next to each other. You can now create a linear array. You may have to add a hexagon at the end of the process to complete the pattern. This gives you a nice hexagonal pattern, suitable for modeling an off-the-shelf hexagonal patterned material. If you are performing a manufacturing operation on the hexagons, you will need more detail. The patterning should still work.
A pattern of hexagons is probably not that hard a hit on your performance. Curves are worse. If you plan to click on an object while in transparent mode, the hexagons are going to drive you nuts. Having a non-hexagon configuration will save you and your co-workers much grief.
Do you really need to see hexagons on the drawings? If not, consider modeling the top and bottom panels the way they are seen, and modeling the core as a solid with a very low density.
JHG