CustomPress custom field & Gravity Form integration

Hi there.

We've spent a lot of time creating a complex directory listing for a client's website (they currently have over 80 listings on the site). The directory was built using custom post types and custom fields created with CustomPress. The client now wants to be able to let the users create the posts themselves using a Gravity Form front end to create a draft of the post.

I've seen a tutorial on how to integrate the 2 (which is fine), however when the custom fields were created, the option for "Allow for WP/plugins" was not ticked and we can't change it. This means that we can't use these fields in the form (which is required). Can you please let me know if there are any workarounds so that we can use the already-created custom fields in Gravity Form to create the new posts?

Thanks very much for your help!

Kind Regards,