MN/PE6 Form Check

This one has been difficult over the last 6 months, and I'm not at mastery yet. It took a while to build the grip and forearm strength to complete a few reps. 

I've always started by hooking my toes under the bar to make sure that I'm in a full pike (first rep in video), but I'm not sure that would count for mastery. Now, I'm restarting the progression by trying to curl up as high as I can, touch the bar with my toes and start from there (second rep in video). However, I'm still unable to curl high enough to touch my toes to the bar at the top. What is the requirement for mastery?

 

Hey Andrew, I'm looking to the first rep...at 20 seconds....are your knees locked? if not we have a problem. because if you fail the first rep you do not need to train many reps.

Hi Alessandro, I thought my knees were locked, but after reviewing the video again I’m not sure. I’ll try it again and focus on locking my knees. 
Thanks

Alessandro, I tried a test run again today and I am able to straighten my knees fully with some effort. However, I can only straighten them starting at the top of the motion and not at the bar:

 

@Alessandro Mainente, I saw in another post that you recommended hooking your toes behind the top bar to get good positioning before descending. Would it help if I start by doing that until I can pike and touch the bar consistently?

You can consider this position a sort of stretching exercise maybe using some straps to hold the position for a longer time.