I tend to not use glue on leathers because they can and do shrink, and then float away from the glue. Some also slime, and that makes the glue impossible to use.
My thoughts would be to rubberband it to the rock, but do not make the rubberband so tight that it constricts the coral. You need to leave a little wiggle room, or the rubberband WILL cut right through the coral, and you'll have a roaming coral.
I also tend to wedge a soft coral between two rocks (one existing rock in the structure, and a smaller one to hold the coral in place for a few days)..
HTH
ps. that Fiji yellow LOVES brighter lights and LOVES higher flow, so place it accordingly.