You can not choose the post types that both appear in related post results and that these results appear on. You can manually override what related posts need on any given post or page and in manually set the related posts that are displayed.. Choose the post types that can need as related posts results Settings->related posts. Choose the posts types that can have related posts need Settings->related posts. Choose whether single post page or CPT will display related post results under the recommend related post meta box in the director. Manually choose the individual related posts that will appear on any given post page or CPT. Choose image jetpack will use for related posts if onbe will be locate in the post page cpt.. Please note this plugin requires the wordpress posts 2 posts plugin to be installed and activated to automatically set individual related post results... JetPack handles the click work in hands-off fashion so every post gets the automatically. Browse the code recheck out SVN repository or subscribe to the development log RSS....
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