Hi There,
That would be possible by changing the template files of the theme.
May I suggest you a different approach?
Have you considered using The Grid or Essential Grid - X Theme Addons - to diplay your Portfolio items? Both plugins allow you to build awesome grid layouts which look very modern. By creating your grid using portfolio items as a source you would be able to add the grid to a normal Cornerstone page which you can edit as any page.
So you can use that page as your portfolio page instead of the X Template which cannot be edited without hardcoding te template files.
Let us know your thoughts.
Thank you!