Check the Cerwin Vega website, or even call their tech support line, they will be able to give you the specs for the driver.
You should also discuss with them the dimensions of the box you are planning to use, they can help you decide on the port diameter and length if you can use one or more in that size box.
If the specs call for a smaller enclosure you can take up some internal space with foam blocks to reduce the overall space the driver will "see".
Facing down will work, try to keep the distance from the driver to the ground as close to half the diameter of the driver or more. A 12" driver should be at least 6" from the closest reflective surface.
Stuffing a speaker in a box is no guarantee of good performance. Best results are obtained by having the proper sized enclosure and ports.