The CA154 is an extremely cost-effective woofer in my opinion, the only potential drawback I can see is that you're already at 4 ohms, so if you need more SPL you can't readily add another cab without the impedance going too low. But for the money (and weight), the CA154 moves a lot of air and has a nice response curve.
I'd probably put it in something like 3.2 cubic feet net internal volume, and tune it to maybe 45 Hz or so. You'll only be -2 dB at the first overtone of low-B (62 Hz), and the lower tuning frequency gives you better fartout resistance than the 55 Hz tuning frequency in Eminence's published 3.75 cubic foot design. Two 4" diameter ports, each 6" long, will get you there.
If weight is an issue, I suggest 1/2" (12 mm) Arauco plywood from Lowes, thirty-something bucks a sheet ballpark. Note that bracing becomes more critical as your plywood thickness and weight go down. Butt joints are fine if you glue & screw them, that's what I do for prototyping, with a good countersink bit and #6 x 1.25" drywall screws (cheaper than wood screws). Use "corner clamps" to hold your joints square while you glue, drill, and screw. If there's a flaw in the wood such that getting an airtight seal is questionable, make some putty by mixing sawdust and glue (assuming you're using wood glue). And after the initial assembly, run an extra bead of glue around the joints from inside the box.
Good bracing can make your DIY build better than a roughly equivalent commercial cab. Ideal would be a window brace that goes around the cabinet at roughly mid-height, and you'd have to bignotch the brace to allow for the woofer frame and magnet. This would adequately stiffen all four vertical boards. Then glue 2.5" wide plywood strips edgewise on the top and bottom in a "+" sign pattern, butted/glued against one another in the middle. Also, do similar edgewise bracing between cut-outs. So if your woofer and port cut-outs are on the front panel, plan on some extra edgewise bracing there. The front panel is subject to the strongest vibrations so pay the most attention to it.
If you can do internal ratios of 1: 1.62 : 2.62, that would be great. I have used such ratios in studio speakers, but never in a bass cab because it just doesn't end up being as practical. Another set of ratios that works well is 1: 1.26: 1.59. You might be able to get away with no internal damping (foam glued to inner walls) with these ratios, which in turn results in a little tiny bit more low end energy.
If you really want to get fancy, use three 4" diameter PVC pipe ports on the back of the cabinet, in a symmetrical row, with the middle port centered behind the woofer magnet. You may have to shift your window brace location to accomodate the ports; it's more important to have that middle port centered than to have the window brace exactly on the midline. Each port is 6" long, and make the cabinet deep enough to allow at least 2.5" of clearance between the middle port and the woofer magnet. Buy two 4" diameter expandable plumber's test plugs, and verify beforehand that they will fit your ports. With three ports open, the tuning frequency is 54 Hz (big low end, possible fartout issues). Plug the middle port, and the tuning frequency is 45 Hz (medium low end). Unplug the middle port and plug the two end ports, and the tuning frequency is 33 Hz (tight low end).
Learn from your mistakes, learn from your successes, and your best speaker will always be your next speaker.
