Hi everyone, my contractor recently installed a new fiberglass bathtub. He didn't nail or screw the tub flange onto the studs. Is that a proper way to insall a tub? I read some books and they all said to nail it in. When I step on the tub and do a little walk on it. I can feel some little noise and some movements. Im not sure if things will be all right. Thanks very much for your help.