Problem while setting a field as required / not-required using gform_pre_render

Hi,
I'm using 'gform_pre_render' to do a lot of stuff on my forms. This is what I'm trying to achieve:

I have 20 fields (all set as required from back-end). I want to set only the first 5 fields as 'required' when the current user is administrator, and keep all of them required if the current user has some other custom role that I defined. Using the filter, I check the current_user_can('role') and set the 'isRequired' property as 1 or blank according to the role.

In the front end, when the form is rendered, I can see the asterisks disappeared for the fields I set as not-required through my code ( by setting 'isRequired' as blank ), but when I submit the form with them as empty, they still fail the validation and my form doesn't get submitted!
Is there any other parameter from the field object I need to disable? Please help me with this.

Thanks in advance!

Hi Chris,
Thanks for the response!
Yes, it worked !
Just tell me if this is the right way:
I made an array with the inputNames of only those fields which are required when the current user is admin. Then in the 'gform_validation' filter, I looped through the fields, checked whether the current user is admin and if the field's inputName is in the above array, just set its 'failed_validation' property to false, and 'is_valid' property to true.
Is this okay? Do I need to set 'isRequired' to false again, as I'm doing it already in pre_render?
I just don't want anything to go wrong with the form meta or something, hence being sure!

- Rutwick