You can add a dip tube into the *nozzle* on top from the hikoil...measure and cut it to end about 3/4 the way down into tank.
I have done it on mine and it solves the problem of cooling the upper portion of the tank. Don't be concerned with adding hot water 3/4 the way down in the tank...the water will stratify and make it's way up the hotter it gets and not be disturbing all the already hot water up top.
Hopefully you have a union there and don't have to cut your way in.
All the *Big Box* stores carry dip tubes.