With a single 120mm radiator, it's all about CFM airflow over the radiator's fins to dissipate a maximum amount of heat. Try putting fans on both sides of your h80 in a push pull configuration. Make sure the push fan that pushes air into the radiat...
Nice mods. I delideed and lapped the IHS and cold plate, but need to add a 2nd radiator in series. Good idea (!) ... With a lot of vcore, are you running any offsets?