How to encrypt or protect workspace variable(s)

I am developing a Simulink model which will be delivered to the customer as a protected reference model ( .slxp ). I have many workspace variables that this subsystem uses to characterize the model. I have a .m file script that I turned into a .p script that loads the workspace. However, I can still see and access these variables in the base workspace. In-lining some parameters is an option, but not all can be inlined as I want to have some tunable and exposed to the user. I would like a way to script which variables are viewable in the matlab workspace ?