. . . does anybody know of a tool, technique or procedure to do this easily, without marring the plastics?

I've finally gutted my (DOA Flyback equipped : ) Blue iMacTripod17 and want to make a pop-top on the back end of the hack. There are some really annoying connectors in there . . .

Does anybody know what the average diagonal of the pixelated portion of the visible 16" diagonal of the CRT would be? 15" perchance? :?: