I need to install a window A/C unit on a sideways sliding window. The window must be open to do this. The A/C unit sits at the bottom, leaving the entire top part of the window open (and unable to be shut due to A/C unit). Any ideas on how to seal off the top part? I was thinking of trying to get sort of clip to hold a piece of custom cut plexiglass to fit in that hole. Any other ideas on how to handle this problem? Please also send your response to nama878 at gmail (dotcom)