I think this looks pretty good. Someone with a more experienced eye may have more to offer, but all I really saw was that you look a little tentative hitting the bottom. I thought you might be a hair high at first, but I think you're ok (after going frame by frame) though the plate partially blocks your knee.
If it's truely a 1RM I'd do it in the rack with the pins set. You know, just in case it turns out your 1RM is 344.