(giggles) Double post take care of.
In your sketch he looks like he is going to fall over to the left.
I don't look at other photos to 'copy' their poses. I look at specifics. Like for instance in your sketch. Look at a photo where some one is kneeling like yours and see what is wrong with yours compared to that of the photo. Take pics of yourself and use them for reference. You won't be using someone elses post that way. I do that with WS and our dogs.
As for suggestions:
His arms need more detail and an elbow joint. Look at arms and the way they are shaped and where they bend etc. The same with legs. The torso as well. I don't look at the WHOLE picture I look at parts of it and then try to improve one at a time. They eventually all come together.
And I know you know practice is going to be the best advice someone can give you and that is only because that is what really helps. Practice doing arms, hands, heads, feet, legs etc.
For the legs, the one kneeling I think the foot should be more behind its leg and the leg should be more to the left to balance the body.
His legs also look too short for his body. Lengthen the legs more. The foreshortening of the one looks fine. Just make the viewable part longer.
Hope that helps.