The dip on the desk that I am thinking about using is at most 1/4", so I can shim it. I was thinking about MDF, but since I haven't used it I didn't know if it would stay flat without the braces.

And as for building at work, my supervisor is in another state. He comes to town about 1 time a year, and that is usually to another city. And since I have all kinds of time on my hands, building a plane would be a great way to pass the time. If I could get a cell phone to work at my house, I could work from home.