How to call the class of a page model where template name is "article.text.php"

I’m wondering about the name scheme for a page model where the template is called something like article.text.php.

Here is my current setup (that doesn’t seem to work):

site/templates/article.text.php
site/templates/article.gallery.php

site/models/article.php

where the last one contains the following php

<?php
class ArticlePage extends Page {
    // some class functions
}
?>

This doesn’t work. I also tried the following setup:

site/templates/article.text.php
site/templates/article.gallery.php

site/models/article.text.php

where the last one contains the following php

<?php
class ArticleTextPage extends Page {
    // some class functions
}
?>

which does work. Has anybody done this before? I would really like to use one class for my article pages as the differences only result in different theming (Of course it would be also possible to put everything into a article class where the classes article.text and article.gallery are inheriting from but it would be easier to just go this way).