I also thought about that during I create the holder, but it is not necassary. Because of the overhang of the spool the force pull at the upper clip and the back of the holder pushes against the screen brace. But the problem with the clip at the bottom is the extruder, if you print bigger objects. Is there enough space between the extruder and this clip + 1.75mm filament at Z>=200? And check, if the filament didn't touch this bottom clip during X moves at Z>=0.