I'm stuck. I can arrange four radio buttons in a square layout with this code:

RadioButtonBar["A", {"A", "B", "C", "D"}, Appearance -> "Vertical" -> {2, 2}]

That's exactly how I want the layout. However, when I place it inside a FormObject, I get unwanted displayed code or I can't get the radio buttons to retain this square configuration:

FormObject[<|
    "CHOOSE: " -> <|
        "Interpreter" -> {"A" -> 1, "B" -> 2, "C" -> 3, "D" -> 4},
        "Control" -> 
     RadioButtonBar["A", {"A", "B", "C", "D"}, 
      Appearance -> "Vertical" -> {2, 2}]
      |>
  |>]

I did ask the Notebook Assistance Chat, but it was not helpful helpful in this case (though it usually is). It seems I've made a mistake and don't understand some nuance of FormObject that would make this work. So I appeal to you all. What am I doing wrong?

Thanks in advance,

Mark