Use the same holes. Make sure you get the speakers wired so they're in phase - ie, the move in sync instead of one going out while the other goes in. A good way to test it: once you have it wired up, plug in a speaker cable and touch a 9v battery to the contacts on the free end of the cable. That's a DC voltage, it'll make the cones move in one direction and stay there. Make sure they both go in or both go out. Doesn't matter which, you can change that by flipping the battery around.
Also, if you're not familiar with it, look up the differences between parallel and series wiring. You'll need to make sure you get it right or the cab will have the wrong impedance.