Hi Matthew - I have followed the iFixIt instructions twice for the iMac screen's disassembly/assembly verbatim. To no avail. My customer has had the screen fall off twice! I was very embarrassed and eventually had to buy a used iMac for them. I used 91% isopropyl alcohol to remove the adhesive (twice) and used iFixIt's adhesion strips for re-assembly. What is absolutely miraculous is that the screen is fine despite (during one of the two failures) it falling 3 feet to the floor from a desk! No cracks/dings - nothing! The video cables were fine as well which absolutely stunned me! I have decided to sell the iMac noting to the future buyer that the screen needs to be re-attached. I am giving up on iMacs from this point forward for repairs.