Upper back in planche progressions

What is the current recommendation for sPL progressions such as PPL and ePPL regarding upper back rounding? Should we be thriving to keep our upper back relatively straight, as in the course videos, or is a kyphotic upper back just as good? I personally prefer the more flatter version that you typically see in actual planches so that is what I'm striving for.

@Coach Sommer

Hi Petri,

Always focus on protraction.  The degree of protraction achieved is merely representative of that particular athlete's inherent physiology.  

Make no mistake.  The athletes in the course videos are protracting strongly.

Yours in Fitness,

Coach Sommer

Thanks, Coach. Not something to worry about then.

You may remember my seemingly endless trouble with a lagging planche. Shoulder issues aside, I have finally begun gaining measurable strength in the progressions by dropping back to test back up (again) with an emphasis on a flat, straight bodyline with strong depression, which kicks in my lats, then locking in the protraction and then leaning. I prefer to see it done this way because I have seen my own bad habits mirrored in other people, where a very rounded back can cover up a lack of protraction. It's probable I just don't have the experience to pick the finer details in this; someone like Coach can certainly glance at someone and assess/fix subtleties on the spot. For me, I need to be a little over-conservative to get the result