CrossFit Seminar Staff member James Hobart demonstrates the strict chest-to-bar pull-up, which is exactly like the strict pull-up, but you need to pullyourself higher, so that your chest can touch the bar, rather than just getting your chin over the bar.
It is worth including this extra bit of height when working your supported and negative pullup progressions, so that you build up strength in this extra range of the movement sooner, rather than later, especially if you would like to perform a muscle up in future.