Ok, got the acrylic parts list finalized, but before I send it off to the laser, I figured I should double check my measurements by making a 1/2-size model. I went back and rearranged some things to make room for fans and to facilitate better airflow.
Here's an overall look at the main acrylic parts. There are many more smaller pieces, spacers, and tubes that I didn't bother itemizing for the mockup.

First I thought I would print out a full-size outline of the bike with a picture of the motherboard in place.

Then I tested the 1:1 scale with an actual ATX board, and my qualifying product, a Cooler Master Silent Pro 850w power supply.


Final overall length is 38".
After getting a glimpse of the actual size, I proceeded to make the 1/2 size model. I only cut out the more important layers surrounding the components.

Peering down into the component area, you can see the lower IO plate.

The 1/2 size motherboard with two GTX580's in SLI:


The mobo and cards in place:



So far so good. Looks like things might actually fit as hoped. I'll go through the parts one more time and add some cable pass-through's and tubing holes, then I can finally send it off. Next update will show the acrylic parts when I get them in. 'Til then!