After training this movement for 7 Month without any big progress, I feels like I have found a good way for me to progress.
Thanks to the foot stop, I can't cheat at the concentric Phase and have to stop when I can't hold good form.
I Think this was the biggest problem. Also i reduced the Frequency from 6 to 4 times Foundation a week, which works better.
If you have Ideas for improving Form, Thank you!
https://www.youtube.com/watch?v=KH8oifuqDrY&feature=youtu.be