Problem there is the low back is not fleshy and you would have a veritable LUMP in the low back. Uncomfortable. Noticeable. Ugly. AND Karen could give you thoughts about bikini or swimwear on that point.
The gluteous is offered because it is fleshy and can conceal presence, be more comfortable, and on and on. I know a patient with a chest install and she was concerned it would show in plunging necklines.... yep it does, and she wears it as a badge of hard battle fought.
You have alternatives within reason with your doc depending on insurance willingness to compensate.
To the lowrise bizzers,
Mark56