Creating a custom back panel

Remember that your PCI cards will be attached to the back panel as well as the motherboard if you base it off the traditional style, so things need to be lined up just so. You should decide ahead of time whether you plan to place your power supply on the rear panel like in traditional systems, or elsewhere. The power supply is typically placed on the rear panel because of the power cable that runs from it's posterior surface and for aesthetic reasons. You should set all of the components that will need rear panel access together in the configuration you plan to install them in to identify any problems ahead of time. It would also be a good idea to insert your PCI cards in their respect slots as they will play a big role in how you arrange your equipment. The best thing to do it take out some paper, pencil, and ruler and start collecting measurements, then you can sketch out some examples to see how you are going to pull it all together. Start with the motherboard. Dimensions you will need to identify include the distance from the top of the power supply to it's base (medial edge in this scenario) so you can identify where to mount the Mb. The Mb will be mounted on some sort of surface usually with small risers lifting it off of the surface to keep the electrical contacts on the back clear of anything that may cause a short-circuit. So build your Mb mounting plate first, add the risers, and mount the Mb so that you can take precise measurements of it's rear ports and access panels with respect to the floor, superior, and both lateral aspects of the rear panel. You can also measure the same dimensions for the PCI cards with respect to all four edges of your rear panel.

In the above image, look closely at the edge where the PCI card inserts into the Mb and note that the PCI bracket is too close to the mounting plate thus adjustments must be made. Next, you need to note that there is a difference in depth between the I/O ports and the posterior surfaces of the PCI cards from the actual surface of the rear panel. The PCI cards have that "L" shaped bracket on their posterior edge to provide a mounting surface with a set-screw for each card within the case. This "L" shaped bracket moves their posterior surface forward about 1/2 an inch. So you need to be aware of this distance to properly design a rear panel that will precisely fit all of your components and provide a stable mounting mechanism for your PCI cards. One way to measure this distance is to use a classic "t-square" which is a ruler with a 90 degree angle bend. Place one edge of the t-square up against the lateral edge of your Mb so that the other runs parallel to it's posterior surface. Now you can use this edge at the posterior surface as a reference to measure how far your PCI cards and I/O ports will be from your final rear panel surface. Now you should have most of the measurements you need to make a trial panel out of something rigid yet disposable. Mark and cut all of your access panels for the components and check to see if everything is correct by mounting your components as they will be in the final build and placing the mock rear panel in place.

If done correctly, with your rear panel mounted on the frame and the power supply mounted flush against the rear panel, your I/O ports and PCI cards will be about 1/2 inch anterior to the rear panel's surface. Now you need to design a rack-mounting structure to secure your PCI cards to while they are inserted in their respective slots. You can measure and build your own, but in this example I simply cut the frame off of an old discarded case and trimmed it to fit my rear panel.

As for the I/O ports, I built a spacer from scraps of plexiglass after tracing the shapes of the various ports in the I/O panel and mounted it on the interior surface of the rear panel.

As you can see, everything lines up good so the fundamental architecture is finished. The rest is a matter of finishing work to match the rest of your case.

The above mockup does not include the I/O plate.