ok i got you ; )
Maybe I should have said "don't let the knees drift forward TOO much".
If you stand straight, and then just bend at the knees, they will go forward and down. You can never break parallel if the knees are going lower and lower. Everyones relative lever lengths are different. The exact stance and mechanics of the lift will be individual. You have to figure out what is going to be best for you.
You can't expect a new complex lift to feel perfect the first day. It will take several weeks to start feeling good. It takes years to really feel perfect.