The not implemented does come from what h2xs generates however you might need to do some massaging of the code before you can actually do something. I have run h2xs on vendor supplied headers and got just my defines and none of the functions. It could be that you are suffering from the same problem!

As well, much of the XS work that I have had to do was not with simply exposing the functions in the API. It was finding a logical way to take the various datastructures that the API uses and making them make sense in the world of Perl.