Double decker cage made into a big single cage

[Dopey]

I have a double decker cage that I would like to make into a single cage. The problem is that once I take out the two middle grates and the middle tray there is a large opening that I'm afraid my Severe Macaw can get through. I have some Acrylic in my garage that I could cut to fit the opening but I was wondering if anyone else had some ideas that worked for them.