Having trouble keeping legs at 90 degree HBP / PE12 (Russian L Dips)

Here is my Russian L Dips

 

http://web.stagram.com/p/768040870565977225_31651094

 

I'm having trouble keeping my legs 90 degreess all the way, any tips on how to work on that? critique my Russian L Dip at the same time would be nice too

you can choose to balance the lean with the hamstring flexibility.

1-lean back vertical and press up verticale requires less hamstring flexibility

2-lean a little bit forward on both ascent and descent requires  more flexibility

my preference is....master both!