cannot get "active-trail" on my customized book menu

Hello! I was using this module to make my customized book menu look totally awesome with jQuery effect. I was able to use the API of the module, following the author's documentation here: http://pixelclever.com/official-documentation-jquery-menu-api.
I would say the that was a great documentation! However, I was having a hard time figuring out how to correctly implement the $trail argument.

Here I was able to create my menu http://screencast.com/t/DhO49VunQs,
displaying correct hierarchy and expanding the section when the parent book page is selected http://screencast.com/t/0e2MWDAl4mb
BUT closes the section when a child page is selected http://screencast.com/t/9JASEOJT

I also realized there are a lot of issue about this, but I could find my case, if not unique, unusual.

I tried to give the $trail the best match to $menutree array, as per instruction: http://screencast.com/t/h7RnGkDuNTNa. I attached here the value of my $menutree:

How should my $trail look like to make the "active trail" work? Can anyone help me? Thanks!