Master Profile - Clarification on inheritance model

I am asking this question in order to clarify my understanding of the Master Profile model and whether it is STATIC or DYNAMIC.

Does Clarizen:

1) Simply create a COPY of the Master Profile at time of Custom Profile creation and then any change to the Master Profile would only affect NEW Custom Profiles created?

2) If not, then does that mean ANY configuration changes to the Master Profile will propagate across ALL Custom Profiles overwriting ANY "customization" within that Custom Profile? 

I can understand NEW items ADDED to the Master Profile being pushed across all Custom Profiles, such as App Deployment; but what about EXISTING options, fields, etc. Remember, we are not talking about DATA or VALUES, but rather configuration or "look and feel" items like Navigation Options, Fieldsets, etc. So what happens if you decide to change how a project fieldset displays in the Master Profile? Does it push across all Custom Profiles? Or only affect NEW Custom Profiles? Because Custom Profiles can change their project fieldset display...

Finally, what about the inverse? If you decide LATER that something that existed in the Master Profile should NOT exist in ANY Custom Profiles and you remove it? Does it remove it from ALL Custom Profiles or does it leave it and then you have to manually remove it?

This would imply that Custom Profiles are STATIC copies and only aggregate NEW items that do not exist, so my concern is about items that already exist and if it is DYNAMIC and re-configures anything.

I would test this out myself, but anything I muck around with in the Master Profile might cause problems. Might be cool to extend the TRIAL PERIOD to 1 year for existing customers, so we could CREATE-DESTROY in our own individual sandboxes. These types of activities are very destructive and would allow technical administrators to understand your platform better, since we look to test these technical nuances. :)