Protected Content: URL Group protection does not allow you to select membership tier

I'm using CoursePress. The courses are set as FREE. I want users to pay a monthly subscription to access all courses. I'm using Protected Content to achieve this.

Here is the challenge:
- CoursePress courses and individual units do not create actual pages, that Protected Content recognizes in the "Protected Content > Pages" tab.
- I was told to use URL Groups to get around this problem. However, when you use the "URL Group" tab the URL Groups listed only offer a simple member/not-member protection. There is no option to select WHICH member tiers can access each URL Group.

I need the visitor to be able to browse/view:
1) The list of courses
2) The units within a course
3) Limited Units that I select as viewable for free

I need tier 1 (Basic) subscribers to view:
1) All of the above
2) All Units in selected (limited) courses
x) No access to Unit pages with Assessment questions
x) No access to Discussion
x) No access to Workbook

I need tier 2 (Premium) subscribers to view:
1) All of the above
2) All Units in selected (limited) courses
x) Full access to Unit pages with Assessment questions
x) Full access to Discussion
x) Full access to Workbook

Protected Content works beautifully with regular WP pages, but it's not so easy with CoursePress unit and course pages.

Please let me know how I can accomplish the objectives above.

Thanks in advance!