What you probably want to do is use the ViewLevel plugin. This way you can make any posts members-only, as opposed to the entire blog.
In aMember you won’t need to specify a protected folder if you use the ViewLevel plugin. Be sure to buy the WordPress plugin. Once you have that installed, you can set the user level of all subscribers fro mthe aMember control panel.
When writing a post you’d add a custom field ‘viewlevel’ and a value that matches the user level you chose in the aMember settings.
There’s quite a bit of configuring, but it’s pretty straight forward, just lots of clicking. There are some instructions for adding code to your theme so that users can login to both WP and aMember, and other nifty features depending on how ambitious you feel.
If you need guidance I’ll be checking back. I’ll try to answer any questions you may have. If you’d like more hands-on help I’m also available for hire.
Good luck!
