Customize tinymce 4.0.5 styleselect toolbar menu

Question

I'm trying to customize the default styleselect toolbar menu so I can add to it a custom menu element. The idea is to place font size as a styleselect submenu:

I initialized a TinyMCE 4.0.5 in the following way:

tinymce.init(
{
    language_url : '/webobbywebapp/js/tiny_mce/language/es.js',
    selector:'textarea',
    plugins: "image, link, print",
    toolbar: "styleselect | undo redo | removeformat | bold italic underline |  aligncenter alignjustify  | bullist numlist outdent indent | link | print | fontselect fontsizeselect",
    menubar: false,
    statusbar: true,
    resize: true
});

As I'm not able to find how to customize the default styleselect menu I'm also trying to create a complete new menu where i can add font size control. But I don't want to show any toolbar, I want a single menu bar.

EDIT: Right now I'm trying to modify the styleselect menu using the following code, but fontselect and fontsizeselect appear disabled

,style_formats:
[{
    title: "Headers_",
    items: [{title: "Header 1",format: "h1"}, {title: "Header 2",format: "h2"}, {title: "Header 3",format: "h3"}, {title: "Header 4",format: "h4"}, {title: "Header 5",format: "h5"}, {title: "Header 6",format: "h6"}]
}, 
            {title: "_Inline",items: [{title: "Bold",icon: "bold",format: "bold"}, {title: "Italic",icon: "italic",format: "italic"}, 
            {title: "_Underline",icon: "underline",format: "underline"}, {title: "Strikethrough",icon: "strikethrough",format: "strikethrough"}, {title: "Superscript",icon: "superscript",format: "superscript"}, {title: "Subscript",icon: "subscript",format: "subscript"}, {title: "Code",icon: "code",format: "code"}]}, 
            {title: "_Blocks",items: [{title: "Paragraph",format: "p"}, {title: "Blockquote",format: "blockquote"}, {title: "Div",format: "div"}, {title: "Pre",format: "pre"}]}, 
            {title: "_Alignment",items: [{title: "Left",icon: "alignleft",format: "alignleft"}, {title: "Center",icon: "aligncenter",format: "aligncenter"}, {title: "Right",icon: "alignright",format: "alignright"}, {title: "Justify",icon: "alignjustify",format: "alignjustify"}]}, 
            {title: "Classes", items: 'fontsizeselect'},
    {title: "dddClasses", items: 'fontselect'
}]

Answer 1

Finally, adding the following code did the trick:

    ,style_formats:[
         {
           title: "Headers",
           items: [
             {title: "Header 1",format: "h1"},
             {title: "Header 2",format: "h2"},
             {title: "Header 3",format: "h3"},
             {title: "Header 4",format: "h4"},
             {title: "Header 5",format: "h5"},
             {title: "Header 6",format: "h6"}
           ]
        },
        {
             title: "Inline",items: [{title: "Bold",icon: "bold",format: "bold"}, {title: "Italic",icon: "italic",format: "italic"}, 
            {title: "_Underline",icon: "underline",format: "underline"}, {title: "Strikethrough",icon: "strikethrough",format: "strikethrough"}, {title: "Superscript",icon: "superscript",format: "superscript"}, {title: "Subscript",icon: "subscript",format: "subscript"}, {title: "Code",icon: "code",format: "code"}]}, 
            {title: "_Blocks",items: [{title: "Paragraph",format: "p"}, {title: "Blockquote",format: "blockquote"}, {title: "Div",format: "div"}, {title: "Pre",format: "pre"}]}, 
            {title: "_Alignment",items: [{title: "Left",icon: "alignleft",format: "alignleft"}, {title: "Center",icon: "aligncenter",format: "aligncenter"}, {title: "Right",icon: "alignright",format: "alignright"}, {title: "Justify",icon: "alignjustify",format: "alignjustify"}]}, 
            {
                title: "Font Family",
                items: [
                    {title: 'Arial', inline: 'span', styles: { 'font-family':'arial'}},
                    {title: 'Book Antiqua', inline: 'span', styles: { 'font-family':'book antiqua'}},
                    {title: 'Comic Sans MS', inline: 'span', styles: { 'font-family':'comic sans ms,sans-serif'}},
                    {title: 'Courier New', inline: 'span', styles: { 'font-family':'courier new,courier'}},
                    {title: 'Georgia', inline: 'span', styles: { 'font-family':'georgia,palatino'}},
                    {title: 'Helvetica', inline: 'span', styles: { 'font-family':'helvetica'}},
                    {title: 'Impact', inline: 'span', styles: { 'font-family':'impact,chicago'}},
                    {title: 'Open Sans', inline: 'span', styles: { 'font-family':'Open Sans'}},
                    {title: 'Symbol', inline: 'span', styles: { 'font-family':'symbol'}},
                    {title: 'Tahoma', inline: 'span', styles: { 'font-family':'tahoma'}},
                    {title: 'Terminal', inline: 'span', styles: { 'font-family':'terminal,monaco'}},
                    {title: 'Times New Roman', inline: 'span', styles: { 'font-family':'times new roman,times'}},
                    {title: 'Verdana', inline: 'span', styles: { 'font-family':'Verdana'}}
                ]
            },
    {title: "Font Size", items: [
                                {title: '8pt', inline:'span', styles: { fontSize: '12px', 'font-size': '8px' } },
                                {title: '10pt', inline:'span', styles: { fontSize: '12px', 'font-size': '10px' } },
                                {title: '12pt', inline:'span', styles: { fontSize: '12px', 'font-size': '12px' } },
                                {title: '14pt', inline:'span', styles: { fontSize: '12px', 'font-size': '14px' } },
                                {title: '16pt', inline:'span', styles: { fontSize: '12px', 'font-size': '16px' } }
]
}]