Try this.
Impromptu drawing of an idea that is cheap.
Just like the plans , just drill 1/8" hole in at least all four corners per sheet of plexi.
The holes in the middle of the sheets are optional, but recommended to give the middle some support as well.
Drill the plexi medium speed with little pressure on it to prevent its' splitting.
Then the pins should hold it enought to keep it from bowing out.
The pins are standard items at nearly every hardware store.
They are straight, solid and have a small ball bearing in the end that is used as a binding or friction type holder to keep them in place.
If the wood won't hold, then you may need to upgrade with aluminum "C" channel, also available at nearly all hardware stores.
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