After some fist try testing with the new Portal-Stack from @joeworkman, I could not get any results with a RW7 project. The content was not shown, simply blank, in preview. On the page with the portal-out stack, the content after the stack was missing as well.
So I tried the Portal Demo-Project with RW8. In this Project the portal in page showed a “parse error”:
Parse error : parse error in /private/var/folders/53/_gzqdk1j6vn5x_ksh_gxgq9rmd9zyx/T/com.realmacsoftware.rapidweaver8/RapidWeaver/5403/document-0x7fd403d31f40/RWDocumentPagePreview/rw_common/themes/Portal/portal.php on line 67
and the portal out page showed the normal content and a parse error as well:
Parse error : parse error in /private/var/folders/53/_gzqdk1j6vn5x_ksh_gxgq9rmd9zyx/T/com.realmacsoftware.rapidweaver8/RapidWeaver/5403/document-0x7fd403d31f40/RWDocumentPagePreview/rw_common/plugins/stacks/portal.php on line 67
On this portal out page, the footer is not visible (not even an error for that portal out stack). So this was somehow similar to my own project in RW7. Even when no parse error is shown in RW7.
Since I tried it with RW7 and RW8 (both fully patched and updated), and with even the demo project itself, I am a little puzzled what to do next. Maybe something was going wrong with the installation of the Portal stack? Is there a way to get more debug info?