Restricting access to 'Project Details' page in MS Project Server 2010

I am currently trying to restrict user access to the project details page in MS Project Server 2010.

At the moment anyone belonging to the project managers group can amend the information stored on the project details page at any point.

I have tried changing the access rights of the Project Managers group to 'Read' via:

Server Settings > Project Detail Pages > Project Details > Edit Web Part > Page > Permissions

However after making this change I sat with a user (belonging to the project manager group) to test the system and he was still able to amend and save the project details section.

Can anyone help me understand what I am doing wrong and how I can create the desired page restrictions?

Thanks!