If your shower arm is the wall-mounted, 45°-type, common with standard showerheads, it’s a good idea. Large showerheads, in particular, are a problem because they may be too close to the wall to position properly. Your rain showerhead will still work, but even if the head is adjustable, much of the spread will be lost. Fortunately, replacing the shower arm should be fairly simple; just be sure to check thread size.Ceiling mounts work well but usually require extra plumbing. A 90° wall arm is a common solution. If you want to gain a little height, look for an S-bend wall arm.