I am getting ready to take the step and punch a hole my 10 gallon polar ware and trying to see if there is a height that people have found best?
I was thinking about 2 inches off the bottom?
I would do the lowest possible while still being able to screw the element in and getting a good seal for the coupling/fitting on the pot.
Do you have a dip tube? False bottom? Bazooka tube? All those things need to be considered as well. Mount the element as low as possible without hitting any of those, or the element power box.