mmaattppoo
Adventurer
I have an 01 TJ and have had heat soak issues in the past. The TJ and maybe the JK has a rubber seal that runs across the back of the hood. Pulling off that seal will allow heat to escape. No cutting needed.
I have never had overheating issues with the TJ and didn't notice any drop on the temperature gauge but I do have less issues with heat soak after doing that.
I thought about removing the rubber seal along the back of the hood to improve air flow (nice simple approach...always a good thing), but water ingress onto the engine on a regular basis (and the associated problems that could cause given it rains a lot in Vancouver, BC) guided me to a hood venting option that could be opened and closed as needed....esp. when it's pouring rain. The addition of a pusher fan improves upon the passive venting when driving slow on long climbs and in summer bumper to bumper traffic when there is little airflow through the grill and over the hood.
I've never overheated, but after reading some very disturbing posts about transmissions overheating (burning JKs to the ground) and being concerned about heat soak wear and tear while driving in warm summer conditions I took a few measures to address the issue: 1) added an engine driven fan (moves serious air all the time at the cost of 0.5 - 1 mpg); 2) added a MOPAR factory transmission cooler seriously reduced transmission fluid temps for the 42RLE auto I'm running; and 3) added a pop-up hood vent and fan.
As you've noted, venting alone doesn't really show up as decreases in any measured temperatures from the engine's perspective (esp. since coolant temperature is governed by the JK's 195 deg F thermostat), but wear and tear on plastic and rubber parts should be reduced while running. Heat soak after the engine is turned off will still happen but there's not much one can do about that on a day to day basis save opening your hood ever time you shut the engine off or adding hood louvers that expose the engine to the elements on a regular basis.