I have a custom designed desk for my office that I had somebody help me fabricate. During that time I realized that, if you use a thick piece of hardwood, you can completely skip the inner legs. In my case it is 1.5" cherry wood.
Knowing that now, I've realized there are other benefits like my monitors shaking less because the desk is so rigid. I'd definitely recommend a solid, hardwood surface to anybody looking to get a custom work desk setup!