How do I write a Photoshop Extension (8BX) plugin?

Question

The Adobe Photoshop CS3/4 SDK has a lot of examples for Filter, Import, Export, etc plugins but I haven't found anything that illustrates how to write a 8BX plugin.

The reason is, I need to write one is to add a new drop-down menu to the Photoshop root toolbar (where it displays File, Edit, Image ... Window. Help drop-down menus). I have seen a product like OneSoftware install an 8BX plugin into Adobe Photoshop CS3\Plug-Ins\Extensions directory that causes PS to add adrop down menu for OneSoft. That suggests this is a solvable problem :-)

I tried by changing an existing plugin in the SDK samples but no go. Specifically I modified the resource file:

resource 'PiPL' (ResourceID, plugInName " PiPL", purgeable)
{
 {
  Kind { **Extension** },
  Name { plugInName "..." },
...

Despite using the Extension Kind, PS never loads the plugin. It doesn't generate any compile-time or load error either.

Does anyone have any ideas on how to go about doing this?