Aha! I can log into the forum again 🙂

As I am now able to log in, I will give you a quick analysis. In particular, I am looking at the overhead shots played at 5:30. I know you asked about the posture/.positioning specifically, but I will give a full analysis anyway. Pick and choose what is useful feedback for yourself (if any!)… here we go:

Grip: you appear to be using a basic/neutral grip. This is good 🙂

Arm action: You appear to be using a good arm action. You are making use of the correct muscles (forearm muscles) and are getting a good contact it would seem. Well done!

Accuracy: The smashes you have highlighted are all going with good angles in good places. I haven’t watched the rest of the video, but if they are all aimed at your opponents hips, then you are doing very well.

Contact height: You are reaching up quite well for the shuttle, but could possibly take the shuttle sooner (NOT necessarily higher – just try to reach it even earlier if you can).

Racket carriage: just before you hit the shuttle, you have a good “ready to hit” position with both arms elevated. However, whilst you are moving, you do not have this racket carriage. Your racket and arms are both lower, until you get into position to hit the shuttle, and then you get the arms ready. As a coach, I would want to see moving in the same position as you have just before you play your stroke – gets those arms and that racket up! Being ready to hit as you move is very important if you play at a faster pace against better players – you won’t have time and will end up taking shots late unless you make it a habit (on all shots, not just overheads!).

Racket action: When you are about to hit the shuttle, your racket dips down below your head, and then you perform your backswing – this additional swing is unnecessary. People use it to try and generate extra racket head speed. In reality, it may affect your shots accuracy, and is one of the things that may stop you from playing a shot quickly enough if you play against better players at a faster pace. I suggest making the swing shorter and simpler is always a good thing, and helps skill mastery by eliminating unnecessary movements. Badminton is a game of precision, and anything that may affect precision should be eliminated where possible. Try to lock your racket into a stationary position before you hit the shuttle, you may get a cleaner/better contact as a result!

Movement: You are making use of your reach alright 😉 Watch what happens just before the overhead at 0:10. What moves first? Basically you move your head as you watch the shuttle. And then when you can’t keep your eye on the shuttle anymore, you arch your back. And THEN you start moving. This means you are moving very late, which results in you not getting as far back as you could, which leads on to my final point…

Contact point: The big one. You are playing smashes, but you are not behind the shuttle. Behind the shuttle means that if the shuttle is left to land it SHOULD land in front of you. Not on your head. And definitely not behind you! This is caused by several things:
1. lack of movement as mentioned previously
2. habit – you probably always hit this way, and don’t know what it feels like to get behind the shuttle!

The contact point is too far back, meaning you haven’t moved far enough. This does several things:
Sight: Firstly, when you are going to hit the shuttle, it is directly above you, and I can see you looking directly upwards. You probably have no idea where your opponent currently is, just before you hit the shuttle – you can only see the shuttle and the ceiling! If you moved further back, you would see the shuttle AND your opponents court.
Weight transfer: Look at where your bodyweight is going after your shot. You are falling to your left! This is going to affect your ability to remain balanced and get the next shot, your ability to move to the correct location on the court or move forwards if appropriate, and will affect the body weight you can put INTO your smash… which leads us to…
Power: Because your bodyweight isn’t being utilised, your smash will be less powerful than it could otherwise be. Ideally you want your bodyweight going in the same direction as your smash to give it some extra oomph!

I think thats everything. What does this realistically boil down to?

I recommend you try to move a little quicker to get behind the shuttle. This will improve the power in your shots, your ability to target whatever areas you want to target, and help you stay balanced. While you are moving, get that racket ready to hit, and just try to take the shuttle as soon as you can. Its ok to remain comfortable if you are protecting the shoulder, but cutting out the additional pre-swing will alleviate some of the pressure on your shoulder too as it will have less conflicting movements to perform in quick succession. But overall, you have a nice effective overhead it would seem.

Good luck to you!