Your method will work yes. You can also set the min/max cpu speeds in the same area that the option to set max OPP level was available. That will then limit the available CPU speed slider to those settings, so you can home/end rather than scroll to the desired speed. Then per application (for those that don't offer preferred speed dialogs on starting), you can use OVR files (manually made or created via minimenu) to set a preferred speed for that app. In addition emulators like PCSX allow for per game speeds from within the emulator aswell, so long as they fall within your maximum allowed speed. It will use the higher voltage when required and otherwise whilst idle, will remain low and conserve battery as normal, so it wont reduce battery life just for the sake of it.
