Add Custom TiniMCE Buttons to the Second Line?

Does anyone know how can I add my custom TinyMCE buttons on WordPress to the second line instead of the first one?

The problem is that I got more than 10, and they keep grouping to the right braking the WordPress editor.

My solution would be to put some below, but I can’t find any documentation pointing to that scenario.

The code I am using to add buttons to the first line with success is (part) of the following

 ed.addButton('example', {
     title : 'example.desc',
     image : '../jscripts/tiny_mce/plugins/example/img/example.gif',
     onclick : function() {
        ed.windowManager.alert('Hello world!! Selection: ' + ed.selection.getContent({format : 'text'}));
     }

Any comment in the right direction will be deeply appreciated.

Thanks!