Adapted the model from boksbox on cults3d so it was just two pieces and fit the drywall (½") in my basement walls without needing the extra inside frame. The clips instead of being glued on are now part of the print which only requires support for the frame piece. I printed in PETG and fits perfect for the spot I needed and should scale to size with x and y while leaving z alone. Might need to adjust z if you have larger/smaller drywall. This is sized for a 125mm by 180 mm sized hole (about 5x7 inch hole).
The author remixed this model.
I took the model from a few items to just two items to print. The clips are embedded to the frame and front now. Does not have the back plate need and needs to print with supports for the frame piece.