Charles,
Do you mean variable control? That would be ideal, but I may only need to voltage divide from 13V to 7.5V for the 50% efficiency.
I'm not aware of any needed isolation requirements.
The modules are rated at 15Vmax, I am working with a 13V power supply.
Personal use.

Are we talking MOSFETs using PWM control?

Ivan,
I have downloaded the file and am looking at the link.

Thanks