SharePoint Online grouped list JSON formatting

I have a grouped list with 2 columns "Question and "Answer". The list is formatted using the following JSON to format the view. Based on a PNP view formatting sample

{
  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/row-formatting.schema.json",
  "hideColumnHeader": true,
  "hideSelection": true,
  "groupProps": {
    "headerFormatter": {
      "elmType": "div",
      "txtContent": "@group.fieldData",
      "attributes": {
        "class": "sp-row-title ms-fontSize-l"
      },
      "style": {
        "width": "600px",
        "max-width": "100%",
        "margin": "10px 0"
      }
    }
  },
  "additionalRowClass": "ms-font-l ms-fontColor-neutralPrimary ms-bgColor-white--hover"
}

How can I control the width of the additional row (The Answer Column)? The column contains rich text so I can't format it in the column view.

I've tried adding the following but it made no difference:

"additionalRowFormatter": {
    "elmType": "div",
    "style": {
      "width": "600px",
      "max-width": "100%"
    }