[jQuery] dynamically change size of select box

[K Bouton]

How do I dynamically change size of select box depending on the number
of responses retreived froma getJSON
[code]
    $.getJSON("select.php",
      {project:"%"  }, function(json){
        var dropsize=json.length +2;
        var options = "";
        options += '<option value="%">All Projects</option>';
        for (var i = 0; i < json.length; i++) {
          options += '<option value="'+json[i]['project']+'">'+json[i]
['project']+'</option>';
        }
        $("#select_project").html(options);
[/code]
now I want to set the select box to have a size=dropsize
for example if the getJSON returned 8, dropsize=8 and the select would
look like

          <select id="select_project" name="select_project" size="8">

thanks

K