Importing registration with custom questions

[streampipemike]

I have been running a webcast with registration.  We have over 6000 current registrants.  We want to start using Zoom Webinar going forward.  The problem I am having is importing the 6000 current registrants.  I can import their Name and email address. But all the custom fields like Title, Organization..... do not import.   Is this a limitation of Zoom's import?