A great looking box!!
I also make boxes, a lot of boxes of all shapes and sizes, and usually I also make them from BB plywood with my I-Box jig (I know the I-Box inventor), but sometimes I use re-sawn thin flat hardwood board stock. You may already know the following info, but here are what I frequently use when making boxes using the Incra I-Box jig. Hopefully, one or more of these tips will help you. I get great satisfaction when making boxes. I guess that's why I make so many.
I use the Freud SBOX8 box joint blade set. Since buying it I haven't used my DADO blade at all, but will probably use it again for larger boxes. The bottom of the cuts made with the SBOX8 blade are perfectly flat and fit together very well, making great 1/4 & 3/8" box joints
For smaller box joints I use a Freud LM72R010 blade and make 1/8" box joints. It's actually a ripping blade, but with an FTG grind for a perfectly flat bottom cut. The I-Box jig will adjust down to 1/8", but it takes a little coaxing.It's the smallest box joint that can be made with the I-Box jig.
Lee Valley makes some Box Slotting bits that are smaller in diameter than the usual slot cutting router bits
http://www.leevalley.com/US/wood/page.aspx?p=47818&cat=1,46168,46176s Using one of these bits in my router table lets me dry assemble the 4 sides of a box and then just run it around the bit to slot all four sides of the box all the way around without breaking through the box corners. The small diameter of the bit cuts into the box sides at the corners just enough so you only need to slightly round the box bottom or top corners for it to fit perfectly, with no corner gaps or the need for stopped DADO slots in the box sides. It's very fast and easy this way. I usually use large elastic bands or a band clamp to hold the box sides together while doing this.
It's easy to make replacement MDF backers for the I-Box jig from a 2' X 4' X 1/4" MDF Handy Panel that you can find at Home Depot, but just moving the original included backer from side to side or flipping it over and using the other edge will make it last a while. But like I said, I make a lot of boxes..For more backers, I just cut pieces of MDF the size of the original backer using my table saw. Then I set up end and back stops on my drill press to Drill the first hole position. With just the one setup for the first hole and then flipping the piece over and then end to end it's easy to drill all four holes with just the one setup. Then I clear away the stops and countersink all 4 of the holes from the smoothest side of the backers and they are done. I got about 14 backers from just one 2' X 4' X 1/4" Handy Panel of MDF that cost me about $5. Incra charges $10 plus shipping for just 3 of them. I had them cut, drilled, and countersunk in about 1/2 hour. I thought I would have enough to last me a while, but yesterday I discovered that I'm down to my last 3, so I'll be making more of them again very soon.
Charley