Here is what it looks like resting on the door, which should work out very nicely.
 

As you can see, I'm using the shorter latch arm for my application. Also notice the round black piece on the arm. The lock set came with three different thickness' of these shims to help with the amount of clearance the latch goes into. The shim I using is the medium one and they snap into place.
 

I needed a way to keep everyone's hands away from all the wires that will go into this box so I'll be using some 3/16" acrylic for this. The blue lines are where I'll be making a cutout for the latch arm for the lock. And I'll also be adding some 'stand-offs' for the plastic to rest on.
 

I'm drilling holes in the bottom of the box to use more flathead screws in the other end of my stand-offs. Notice I'm using a center drill in my hand drill first. This is the best way to make sure the hole that you're drilling ends up in the exact spot that you want. Once your done with the center drill, then you follow up with your drill.
 

I found some aluminum tubing that was 7/16" diameter laying around. And the tubing already had some 5/16-24 fine threads in one end so I decided to use them. However, the other end of these pieces will have 5/16-18 coarse threads, which I'm taping below. Why two different threads? Because I had some of the coarse bolts already, but I had to buy the fine ones.