Sliding door whiteboard frame

I DAGSed (Is that a word?), but could not find anything close to what I am attempting, so please bear with me.
My wife is a teacher and wants me to make a sliding door whiteboard that fits over the corkboard mounted in her room. Here's a description of the project as I'm envisioning it, question to follow...
Current Conditions:
The existing corkboard is 48" x 96" OD and 44 1/2" X 92 1/2" ID (There is a 3/4" X 1 3/4" Plain Pine frame surrounding) I am NOT allowed to put any holes in the wall. I can get away with screws into the SIDE of the corkboard frame, but not into the face. (She is not going to be at this schoold for more than a couple of more years). The corkboard is securely bolted to the wall to handle the potential abuse of the kids, so additional weight on the frame shouldn't be a problem.
Desired condition:
Mount a frame around the corkboard to give additional depth. Use the 1/8" thick whiteboard masonite available at the BORG as the whiteboard surface. Create a two panel (48"X48" ea.) sliding door. The goal is to have her be able to use the whiteboard with the doors "closed" for lessons and as a projector surface. At the end of class, she can open up one side and the assignments or other information will be tacked to the cork behind it.
Preliminary plan:
I was thinking of using 1X3 pine with a 3/4" rabbet to match up to the existing cork board frame and mitred at the corners to provide the depth. I was planning on cutting two 3/8" deep 3/16" dadoes into the rails to provide the tracks for the sliding whiteboard doors. I'll finish off by tacking some sinple moulding to pretty-up the face. I'll either put some hardware knobs on the masonite panels or rout a 3/4" handle into them to provide her with a way to slide them around. I'll put some graphite or paste wax into the dadoes to make them slide easier.
1. Will there be too much flex in the masonite? I'm somewhat worried about stability while writing and the potential for the doors to fall out of track. On the other side of the coin, I want to avoid as much weight as possible, so if I can avoid plywood backers I would like too. Should I build a frame around the masonite. If so, any suggestions?
2. Is 3/16" a good size for the dado, or should I go with a 1/4" dado? Obviously, if I am forced into using a frame I will need to expand the dado to accomidate.
3. Is the paste wax/graphite idea good enough to provide a somewhat smooth slide? The action does not need to be perfectly smooth, but I don't want her to have to lean into it either.
Please remember that I cannot mount to the walls so weight is an issue. Also, please let me know if I should scrap this idea and go with her "Just cut me a 4X4 board that I can prop on the table idea" She likes the sound of my idea better, but can work with the prop.
As always, thanks.
email address is jay, not junk.
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