Special Permalink structure, anybody?

Hi all,

I need a specific permalink structure for a custom post type.
This is the structure: /%custom_taxonomy%/%postname%/%subpage%/

So in example this would be: /ferrari/f430/ as main information page and /ferrari/f430/specs/ or /ferrari/f430/speed/ as subpages.

The subpages don’t need post edit screens in the backend, it’s database generated.

How would you archieve this?

My current solution uses custom permastructs in combination with the post_type_link filter. I then use Endpoints in combination with the single_template filter for the subpages.

$permalink = '%cars_slug%/%brands%/%cars%/';
$wp_rewrite->add_rewrite_tag( '%cars_slug%', '(cars)','post_type=cars&slug=' );
$wp_rewrite->add_rewrite_tag( "%brands%", '(.+?)', "brands=" );
$permalink = trim($permalink, "/" );
$rewrite_args = $args->rewrite;
$rewrite_args["walk_dirs"] = false;
$wp_rewrite->add_permastruct( $post_type, $permalink, $rewrite_args);

But somehow it doesn’t feel right.