I would like to be able to do the same and have had the same result error. When i add your code to functions.php If i select restrict access by capability in the POD edit group settings and use is_page_(slug) within the allowed it correctly shoes the group within the right page but when content is added within the field and page updated it seems to refresh the fields back to their original state. For example i have a check box that when checked it uncheckes when the page is updated/saved. If i remove the restriction by capabilities and show the field on all pages it works fine.
