Top vent or bottom vent are ok ideas but I like to pick the lid up every half hour or so and sprits my low & slow cooks with apple juice.
I’ve never had a problem with heat loss or overrunning temps.
I cover my probe leads with alum foil and this works 2 ways.. it keeps the probe cables clean and smoke free and just the ends need to cleaned after the cook. And the loose wrapped alum foil seals any air leaks.
Just to clear things up.. new grills have piss poor fitting lids!! If you are lucky enough to have an older grill or a older 18” grill... these lids fit nice and tight and with those you might have a problem with the leads under the lid! Then you would have to go in the air vent or cut a probe hole and use the WSM grommet or some other type.
I think any Late Model Master Touch is fine dealing with cables under the lid without problems.
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