Not sure if this will work but when I had my rollbar installed it went through the speaker holes...had removed the cardboard shelf...to put it back I cut slots out for the roll bar...put the shelf in...then took the pieces I had cut out and glued them back using liquid nails(get it at Home Depot)...very string stuff...I glued pieces of metal (probably 1"x 2") to the bottom of the pieces with the metal sticking out past the edge of the piece...then glued the piece to the shelf...I did it all from the bottom of the shelf so the top was smooth...I had pulled back the carpet...so I just sprayed some fabric adhesive on and glued the carpet back...in your case you should be able to glue some metal pieces across the crack from the bottom...just make sure the metal is thick enough so it doesn't bend...just an idea...