Form to create new post type in multisite install

To use the gform_post_data filter for a specific form you would append the form id to that filter call. For example:

Instead of this:

add_filter("gform_post_data", "change_post_data", 10, 2);

You would do this:

add_filter("gform_post_data_5", "change_post_data", 10, 2);

The 5 in the example above (gform_post_data_5) is the form id.

Now keep in mind that when doing this if you add this to a theme that is shared by other sites then it's going to fire for form id 5 on that site also. You would have to wrap it all in an if statement to see if the site id in the multi-site install is a specific id to force it only to do so on a specific site in a multisite install.