guess the adhesive is not for waterproofing, but for better fit of dispaly unit. lots of customers have "problems" with klicking sound of the display unit, or badly seated displayunits resulting in small gaps between display and enclosure.
thx for the video!
note i was repairing looked slightly different. no antenna on the left and powerbutton/vibrator where differnet parts, midframe is hold by 2 additional tabs inside battery compartment. video was a good addition to this guid, and helped alot ;)