Building a new rack

I am in the process of building a portable studio recording rack that I can use with my electroacoustic works, as well as just about any other possible recording set up I can think of at the moment. I have officially payed for all of the equipment, I just have to wait for some of them to be delivered to the store before I can pick everything up and assemble the rack. I will share photos when I’m done.

Although, according to my math I will have one open space on the rack. For now I am just going to cover it with a cover until I can think of something to fill it. Any recommendations?