Capture MFM Custom Fields

As you may already know, MFM user data is not accessible nor stored in the WP database. This pluggin is awesome and a great start. My question is how do we capture data entered in custom form fields that were created with the MFM?

Our goal is to use either Zapier or WP’s API to integrate with other services. This plugin creates / adds a user into wp database but not the custom fields. Any ideas on how we can modify this plugin to add the data submitted in MFM as user meta data and stored in WP database?