Hi there Stewart.
Your swing looks very familiar to me. A lot of what you do, I'm often doing myself. I play in a few local money events and do quite well so good golf can come from it.
Lets first talk about your setup.
I like to talk about the setup because it's static and easy to change.
The first thing that any good golf professional looks at is the grip. The grip basically dictates everything that you must do in the swing to make the ball go straight. You have a classic strong left hand grip with a neutral right hand. Because the hands are working from these two different conditions, it's very easy for one forearms to take control of the other. However, as with just about anything in golf, good hand eye coordination can prevail.
I would prefer you fix the grip of your left hand. Your left forearm is rotated almost to the 2:00 position. Get it so that your wrist bone is vertical. Your right wrist bone is already there.. so just make it so your wrists are perfectly parallel with each other. Now there is going to be an immediate problem for you with this netural left grip. You aren't going to feel like you are making as strong of a pull down toward the ball with your left. It's going to feel like you have to backhand it. But don't worry... that's what your right arm is for.. and if you let your right arm really make a strong move toward the ball, it's going to feel as if nothing has changed.
With your left forearm being so far rotated, it's made you learn some interesting habits. Again, those habits are formed because of the grip. I believe your takeaway is culprit #1. You've learned to set the wrists very very early. For some people that's fine, but I don't like it. I think you've already established a lot of tension in your forearms and tension is the killer of speed. It is also difficult to know when and where to let go of that tension to square up the clubface.
At transition you haven't gotten much weight on your back foot. That's actually a learned habit from fear. You are afraid that if you stay behind this shot, it's going to be a smother hook off the face of the earth. Your left arm simply cannot stay under rotated through impact long enough to facilitate a straight shot, if you are too far behind the ball. As a result you have learned to stay centered with your weight and not move back much. That way you can easily get to your front foot on the way forward and therefore give yourself less time required to keep your left forearm under rotated. In essence you can PULL with your left arm like a karate chop... if you were still a little bit back behind the ball at impact, you couldn't maintain the karate chop action long enough into the ball... and thus you hook it. Possibly even hit it fat.
As you are approaching impact it sure looks like you've maintained lag well, but with that strong left grip you're practically cheating. The club is comming in very flat which isn't really a bad thing. A lot of people would kill to have the club in line with their right elbow. Sergio Garcia plays from that position very very well...
But I want you to look at the down the line view just after impact.
Notice that the hands have travelled well inside, but the clubhead has not? That's because your left arm has to maintain this karate chop action THAT LONG in order to keep from letting the clubface rotate too much and hook it.
If you look at a player with a neutral grip, by the time the hands reach this position the clubhead has already worked much further along. This is a classic "Block" action. In essence you cannot allow yourself to fully release your angles or else you golf ball will need a left turn blinker. That's major power leakage all to prevent the hook.
And finally your finish.
Now the great thing about the finish to me is that it's just like your setup. It's static. And it can tell us a LOT about how you swung.
First thing of note is the position of the club. Notice it's horizontal? That's because you had to keep your left forearm under rotated. If you had a proper release and stayed relaxed from the ball all the way to the finish, that club would be pointing back down to approximately where the ball was.
I know other members of this board are probably going to hammer me for saying what I'm about to say next, but you're rolled out on your front foot and I dont like that. I know it's common practice now days but it's just another indication to me that you've basically pulled your arms accross your body on the forward swing instead of letting them release. If I were to draw a straight line from where your right hip is down, it's just over your shoe laces. It should be about an inch or two in front of your left toe.
If you think about it, I don't think you could hold your balance with that rolled out foot for a full minute, if you lifted your right foot off the ground. Obviously to hold your balance for a full minute on your front foot, you would want it flat on the ground. That's not so hard to do really, your right hip just has to go more to the right, out toward right field. Right now it's going towards shortstop.
And lastly about your finish... your hands are too far around your shoulders. They should be closer to your head. I don't want them to go UP more... I just want you to finish with them closer to your head. That should put them right over your left shoulder socket. Right now they're right over your left bicep. Again that's because your hands and arms swung ACCROSS your body rather than being released fully. And once again I have to point out that's because of your strong left hand grip.
Honestly though you are athletic enough that this is all very simple to solve. Assuming you want to make these changes at all. As far as I'm concerned you can do just fine with a little tweaking of what you have. A few things here and there to what you currently do, without adjusting the grip, can probably produce some consistency. But those wouldn't be much more than just swing thoughts to get you back on track when you start hitting the ball poorly. The karate chop to the ball with your left arm thought would work great for you. Pressing with the palm of your right hand as Jim suggested is also good.
If you are going to fix your left hand grip then you will have to learn to be relaxed through impact and on to the finish much more than you've ever done before. You'll also have to fix the direction that right hip is going.... and lastly you'll have to learn how to get your right shoulder downplane.
Overall, I say you are a very athletic guy with a good athletic swing. It's very powerful.. hits lots of low trajectory shots. You have a great deal of spin to them. A lot of good players have played good golf with your swing. With a good short game it wouldn't be a surprise to see you playing on the Nationwide at some point.
