Ext.LoadMask configs are not applied

I want to modify the style of the element of a LoadMask, but configs such "style" or "maskCls" are not applied.

My goal is to render the mask message not in the center of the component, but in one corner.

I am using the LoadMask for ajax request like this:

Code:

  Ext.Ajax.on("beforerequest", function(){
        myMask = new Ext.LoadMask(Ext.getBody(), {msg:"Please wait...", style:{ left: "0", bottom: "0" } });
        myMask.show();
  });
  
  Ext.Ajax.on("requestcomplete", function(){
        myMask.hide();
  });