Make video fill screen

Hello,

I am calling a stock heygen avatar via api. This one - https://app.heygen.com/avatars/looks/public?avatarId=1727686832

Here is the JSON I am passing the api -

{
  "video_inputs": [
    {
      "character": {
        "type": "avatar",
        "avatar_id": "Juan_standing_sofacasual_front"
      },
      "voice": {
        "type": "text",
        "input_text": "{text}",
        "voice_id": "68dedac41a9f46a6a4271a95c733823c"
      },
      "fit": "crop"
    }
  ],
  "dimension": {
    "width": 720,
    "height": 1280
  },
  "callback_url": "https://hooks.airtable.com/workflows/v1/genericWebhook/appWIHns7JDFuKZj5/wfln5a4Wi8girWikI/wtrqPOZ3MVFVuSaVW",
  "callback_id": "{id}"
}

I've tried a few different values for "fit" - but no matter what the video comes back horizontal and small, it's outer width edges contained within the vertical aspect ratio and a lot of blank white space on the top and bottom.

What should I add to make this return a filled vertical video?