Preliminary Cabinet Design

I realize that I'm going to need to figure out what kind of cabinet I want to put this amp in before I can begin to assemble the chassis. Because of the style of project box I chose, it looks like it's going to be smartest to make a vertically-mounted chassis (like the old tweed Fender amps). I'm doing it this way for two reasons: because it's going to work best with the parts I've chosen, and because this way I'll have the opportunity to design and build my own style amp rather than completely copying the Vibro Champ. Pride in originality. Below is a sketch of what it might look like, from the rear:

As you can see, the chassis will sit vertically with the tubes protruding towards the floor. 

Another cost-saving feature of this arrangement will be the cover of the project box. Since it can be covered by the back (wooden) panel of the amp cabinet, I don't need to purchase the costly sheet metal cover to match the project box. 

At this point, I am fairly certain I'm going with a 2x8" speaker configuration. However, that can be decided for sure much later, after the amp chassis is assembled. As long as I'm pretty sure I want to make the chassis sit vertically like this, I don't have to make final decisions on speakers and exact cabinet size until later.