Do you plan on running your device only at 300mhz??? Sometimes people have issues doing that, their phone won't wake up and they can't turn their display on. If you start really experimenting, id make sure you don't have anything set on boot. If you insist on set on boot, Setcpu does have a way of creating a file to go back to stock if a problem arises.
I like creating profiles, eg screen off, max speed of 400, or battery <30% max speed 800.
Android overclock has the setcpu governor built in.
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