i do it in another way:

i have a BasePage class - which is a skeleton for other Pages:

class BasePage(rend.Page):
    __implements__ = rend.Page.__implements__
    TITLE = "Common Page"
    docFactory = loaders.xmlfile("_tpl/common/page.xml")
    def render_title(self, ctx, data):
        ctx.fillSlots("title", self.TITLE)
        return ctx.tag

    def render_content(self, ctx, data):
        raise NotImplementedError, "You MUST overload render_content() method!!!"

And BasePage tremplate:

<html>

...metas

<body>

...layout

<n:invisible n:render="content" />

</body>

</html>

And then all of the site pages are using this prototype:

class Root(common.BasePage):
def render_content(self, ctx, data):
return loaders.xmlfile("_tpl/root.xml")

i can return ANY xml-temlate i'd like :)

for example a form or a "form submitted successful" message