I would personally like to see a better purchase on the bar out of the rack. Moreover, when you go into the dip, I've always been under the impression you should bring your elbows down and into a driving position - while still maintaing the rack position of the bar with the front delts.
You look very quick, snappy, and full of vigor with the movement. However, how does it look when you get toward maximal effort? If you have the ability to throw up your ME weights with your elbows high while in a finger tip rack position - more power to you. I, for one, cannot and I wouldn't advise it to those I train. But if you have that ability, I wouldn't change much - the arch issue is a non issue from what I see with that weight. You move the weight like it's nothing. Good work.
All the best,