Hello, our mounting brackets are designed to fit an industry-standard electrical box rated for a fan. We would recommend changing the electrical box. We would not recommend doing any modification to make the mounting bracket fit an electrical box due to performance and safety reasons. We are sorry to hear that you returned a fan. We are committed to resolving any issues with our fans. If you need any help further help, please get in touch with us at 1-888-830-1326 or Customercare@hunterfan.com. ~Michelle