OP
I did the box first, then the cylinder a rough estimate. here is a few linksThat in-spare-tire glassing was genius!! I'm doing the same thing and I was perplexed at how I was going to glass it. MUCH MUCH easier way you have there than I was planning lol!
How did you measure the cubic footage you were getting with the entire enclosure? I looked online for the volume of a Frustum of a Cylinder, which is what I'll be using.