SamPLaT, if you search the forum you'll find that this problem is probably tied in first place with keeping you balance during the Seven Steps, for the most common difficulty.
I know I struggled with it too. Of course when you stop struggling, is when it happens. I've never heard of any variants, just do what you have to do to stay relaxed. Relax and enjoy the harmony and it will happen.
My other suggest, for when you having troubles with any of the exercises, is focus on the energy and not the movement. In this case focus on the energy and not the breathing.
If you relax more, you'll inhale slower and be full as the right time. You won't over inhale, and exhale too quickly. Then rush the movements to keep the synchronizaton. Relax and feel the energy.
You are perfection,
Iam2