A hammer head does not result in a tail slide.
Tail slides with most real aircraft are very very bad things to try. Most planes are not built to have air flowing backwards over them, things like flaps bending and control surface rods bending do to reversed airflow are real possibilities.
A properly done Hammer head does not start at Zero airspeed. Rudder kick happens when still traveling up and Zero Airspeed happens when about Perpendicular to the world, I.E. 1 wing down.
Normally almost full Opposite aileron is applied as you push the rudder, and more forward stick is also applied as the plane wants to sorta of twist on its back. And learn the manuver to the left on American planes, Last year when I was flying a Yak in the Ukraine, forgot the prop went backwards, and they go much slower against the slip stream. Still can not believe the pilot not knowing me put me in an inverted spin.
Rudder kick speed is fairly critical and varies between planes, when I do them for real ( and i have done a lot of hammer heads) you only have about a 5 knot window for the Hammer head to work, to fast and the plane sorta just hangs with the rudder over for a while, then the nose comes down, to little speed and you do not have Roll control of the plane and it normally ends up on its back.
With the most AH planes start by doing them at 50% throttle or less. Full throttle you will have to do them at to high of speed and the top of the arc will not have the correct speed.
I also find them harder to do in a sim vs real life do to feel and the visual you get. But even in a real plane it took me about 20 tries to do one with out ending on my back or nose up in the exit. There is a lot of elevator inputs to keep the plane slicing instead of flopping one way or the other.
HiTech