When you take your sub in to be installed is it normal that they don't mount it or even ask if you if you want it mounted?

When I do get them mounted if I attached the box to the sides of the trunk like a rear tower strut bar would would it act as one?

Also I ended up getting into a car chase with my subs sliding around in the back and took a couple turns faster than I should without it mounted and now the base will randomly hit whenever the radio is on even with music paused. What might this be?

BTW I checked all the connections to my amp and when they did the install they created a ground loop which still hasn't been fixed.

 

hey cmon, help a brother out.