I just pick a spot that is usually in the neck muscle. When it approaches the temp I'm looking for, I probe around the butt with my impeccably accurate BLACK Thermapen. When most of the butt is at the temp I want I pull it from the smoker.
A few small holes in the foil make no difference whatsoever.
Jambo Pit - UDS - Lang 60 (Sold)
18.5" & 22.5" Weber Kettles - Smokey Joe and Mini-WSM - Bubba Keg - #2 La Caja China
Impeccably Accurate BLACK & RED Thermapens
Operation BBQ Relief Founding Member
I am Obsessive Compulsive about BBQ. Google it.