I actually stored my grade 5 overcharged powerplant for my python because heat management became ridiculous, even with an excellent roll. I'm now running an "overclocked" [over documented max roll] grade 1 overcharged power plant instead... as it gives me more than enough power for my PVE combat fit, while also affording decent buffs to my integrity and especially heat management. Easy to get when all you need to make the roll is sulpher, which is very easy to find in quantity.
If you're running a PVP build... I would advise never, ever run an overcharged plant unless you get a miraculous roll that gives you a positive buff to integrity [which is very difficult to roll at higher OC mod grades]. Using a grade 5 OC plant is just asking for trouble... as it will die very, very quickly due toa significantly lowered integrity. For PVE... OCPP's seem to work fine for me.
Just keep in mind... the higher the Overcharge grade... the more heat efficiency you lose, so if you're running weaps with high thermal loads, you'll find yourself have to wait for cooldown unless you use heat sinks. The higher the thermal load the faster you'll reach critical heat levels which will shorten your fire volley.