Figuring things out

So, I'm starting to learn some basic anatomy. I've been recording myself on my Planche progressions and notice my back seem more rounded than the F1 videos show. I've also talked with a PT and strength coach. He mentioned my serratus is very underdeveloped go the amount of protraction I do. He didn't explain anything more than that, but could it be my suprispinatus is taking over causing me to protract and elevate the shoulders? If so are there a few things I could do to shore up this weakness?

I think that an image or a video could help a lot, to check out the correct form

I've seen a lot of my clients exageranting posture before working with me. the reason is that posture os a consequence of muscles activation. extreme rounded back means incomplete muscles activation especially lats, medium and lower traps.