AutoSizingTypeEnum... how to use?

I have this simple script that fills a blank page with textframes:

function makeLorem(length) {
    var result           = '';
    var characters       = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789';
    var charactersLength = characters.length;
    for ( var i = 0; i < length; i++ ) {
      if (i>0 && Math.floor(Math.random() * 6) < 2)
        result += " ";
      else
        result += characters.charAt(Math.floor(Math.random() * charactersLength));
    }
    return result;
}

function getFrameContext() {
  fc = {};
  fc.doc = app.activeDocument;
  fc.margins = fc.doc.pages[0].marginPreferences;
  fc.w_idx = 0;
  fc.h_pos = fc.margins.top;
  fc.h_size = 0;
  fc.addTextFrame = function(t) {
    var productFrame = this.doc.textFrames.add();
    productFrame.geometricBounds = [
      this.h_pos,
      this.margins.left + this.margins.columnsPositions[this.w_idx*2],
      this.h_pos+20,
      this.margins.left + this.margins.columnsPositions[this.w_idx*2+1]
    ];
    productFrame.properties =
    {
      strokeWidth : 0,
      fillColor : "None",
      contents : t + ": "+ makeLorem(Math.floor(Math.random() * 200)+50),
      autoSizingType: AutoSizingTypeEnum.HEIGHT_ONLY,
      autoSizingReferencePoint: AutoSizingReferenceEnum.TOP_CENTER_POINT
    };
    productFrame.fit(FitOptions.APPLY_FRAME_FITTING_OPTIONS);
    this.h_size = 20;
    this.w_idx += 1;
    if (this.w_idx >= this.margins.columnCount) {
      this.w_idx = 0;
      this.h_pos += this.h_size;
      this.h_size = 0;
    }
    return productFrame;
  };
  return fc;
}; 

function main() {
  var frameContext = getFrameContext();
  for (var i=0; i<8; i++) {
    frameContext.addTextFrame(i);
  }
};

app.doScript(main,ScriptLanguage.JAVASCRIPT,[],UndoModes.ENTIRE_SCRIPT,'Insert-Frame-Test');

How can I get the autosizing to work? What I need to do...:

• create a Textframe (works)
• put it into the correct column and vertical offset (will work as soon as I figure out the next step)
• have it set it’s height to fit the content
• measure the height to get the h-position of the next text-frame.

Frame-fitting is set to AutoSizingTypeEnum.HEIGHT_ONLY but InDesign ignores that.