I'm not sure if you have to undo the code changes you made after trying this method. I also don't have any blogs on my test site to test this with
Go to user group manager / supermods
Scroll down to the administrator permissions are
Select YES for can access control panel
Save
Go to user groups / admin permissions
Click on edit permissions (will have to do this one by one)
Adjust permissions (can admin blog and can admin blog permission to NO )
Save
Test and report back here if it works.