fcpx change speed on the fly during playback

Hi,

Is there shortcut or keyboard command that allows you to slow down playback and then it up again to 100% without making the playhead jump backwards or forwards due to the contraction or expansion of the clip? My optimum solution would be to watch playback at 100% then when it gets to some part where I want it to slow down to 10%, I'd hit the 1 key (or similar), then if I wanted to go to 50% I'd hit the 5 key, and when I wanted it back to 100% I'd hit some other key like R -- all without stopping the playback.

I tried the shortcuts for "retime" (50%, 25%, and return to full speed) but these cause the playhead to jump around to different parts of the video (apparently due to the clip getting longer or shorter and the playhead continuing to play at the same spot in the timeline), whereas I just want it to stay in the same spot and either speed up the play or slow it down, depending on my momentary wishes.

Thanks!