Humidor Build Questions

[Stig]

I am looking at building a humidor in my shop to store calfskin drum heads that I make and sell (And if things don't work out, storage for seeral thousand cigars.) to keep them from warping when it gets very dry. If my numbers are correct the unit will be 4' wide x 5' deep and 6 ' tall for a total interior measurement of 120 cubic feet. I have a couple of questions that I didn't find answers to using the search function so.

1. I know that Spanish Cedar is used inside cigar humidors for its ability to hold humidity but I am wondering if there would be any problems using other types of wood because this isn't being used for cigars?

2. Do I need to worry about the wood warping over time from the humidity? I will most likely be using plywood because of the size and function.

3. Has anyone here used a humidifier for a unit this size and if so what type was it and how do oyou like it? The easier to use the better, something to set and forget that would automaticaly regulate the humidity in the box without worry.

4. Any recommendations for the door and how to keep the humidity from escaping? It will most likely be a big plain wooden door with hinges.

I would be interested in hearing from anyone that has taken on a build of this size.