As with any backwards walking action, special care should be taken on the first step of the impetus turn to draw the weight through the foot by working backwards from toe to ball to flat and then ultimately to the heel, without collapsing the weight backwards onto the flat foot too quickly before the body weight arrives over it (a mistake I like to call the "flat tire").

Remember also that the toe of the front foot should peel off of the floor quite early on in the first step, before it begins to draw backwards towards the back foot. Draw the foot back in a linear fashion and delay most of your rotation until after you have closed your feet. Then send your thighs forward towards the lady and stretch your head weight strongly leftward.

Finally, begin to rise onto your toes and extend your left foot side & slightly back. Move your weight backwards onto the foot and lower onto a toe-heel (toe of front foot can remain connected to the floor).

I hope this helps.

Sincerely,
Jonathan Atkinson