Depending on where the weight of the monitor will go, I don’t think it should be a problem.
What I did was to use carpenter’s squares to fasten the two left/right frames to the top. On this picture the top is the one with ventilation holes:
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What you don’t see is that I’ve screewed to top frame to the left/right frame.
The weight of the monitor is on two pieces of wood that is screewed to the sides. Those pieces of wood keeps the monitor from falling back too. On this picture it looks like the weight go to the bottom frame, but that is not true:
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