Is it possible to display Entityform Types using Page Manager and Panels in D7?
What we have done so far, is to reference an Entity-Form in an node type with entityreference.
This works so far. 
The Form will be displayed in the panelized theme and the preview will show up too in the correct context.
But! 


The Preview will not show the labels of empty fields
The submission Page will not show in the correct layout and is still loosing context (even with pm-existing-pages)
List fields are broken, if core Patch https://www.drupal.org/node/1677598 is applied they don't break the form submit, but are empty in the preview and not saved.
Date fields with time are somehow broken too. Time is not safed, Date only when using the PopUp Calender


We decided to use the redirect option instead of the submission page to workaround the layout problem with the submission.
The Preview is still broken and we are trying to get it fixed. 

Conclusion: Entityforms and Panels do not play well together. If we would have know this before we would have built a custom module or used Webform 4.x instead (we are still using webform 3.x in this site but there you don't have the option to use views to manipulate submitted data without loading another bunch of buggy modules!)

Hopfully Drupal 8 and YAML-Forms do a better Job in the future.