I get it as close as possible or the tabbing will fall
in the crack. I make a template out of luan and cardboard tabs before cutting the floor panel. Cut your old upper tabbing flush to the wall and try to save the bottom tabbing and cut about 1" from the wall. Glass the floor to the old bottom tabbing. Then fill the void with West System Six-10 after that sets up, tab the top side to the wall. Make sure you use adhesive calking on the metal lip above the drop floor for an air and water seal.