Do you think it would be possible to sand of a millimeter or so, so the flash could fire? In the photo it seems very close to the point where the flash would be open enough to be able to fire. Or would a millimeter sanded off of a small area compromise the proper functioning of the housing (i.e. no flooding)?
No, it only goes up about 2mm. Meaning, it's still about at least an inch (the entire height of the flash) from going up.