Question about the Paypal Pro Form

Hi I’m hoping that I can get some help with the Paypal Pro Forms.

We allow our users to sign up as a subscriber to our website for free which gives them an S2 member level of 0. We only ask them to provide us with a username, email, first & last name and a password. We then have a paying level which they can update their account access to a level 2 subscription. It is at this step that we want to collect some extra information about them, like occupation, date of birth, address etc.

We have the registration form working how we want it to using the custom fields. But the problem is that when users are already subscribed as level 0 subscribers, the ‘Paypal Pro Form’ that allow users to upgrade from level 0 to level 2 doesn’t allow us to show the custom fields so that we can collect the extra data.

I have had a look at this article here: https://s2member.com/kb-article/s2member-pro-forms/#-customizing-pro-forms and I can see that I can create new fields in the ‘Paypal Pro form’, but I don’t really want to create new fields, I would like to use the same fields that already exist from the normal registration form.

I can also see that the extra custom fields are actually already there in the html on the ‘Paypal pro form’ but they are hidden and disabled.

I have tried to unhide them and remove the disable attribute, but the information doesn’t seem to be collected in the database, when I go and look at the user profile in the normal wordpress area.

Is there some way that I enable these custom fields in the Paypal pro forms so that a submission will pass this data to the database?