In answer to your question Stretch, I've been through several issues with my swing, hips too square at impact, high hands, early extension, backing out of the shot, lifting the arms in the takeaway, the list is endless.
I believe the fundamental of a hitting action whether tennis, badminton baseball or golf is to have the hips open at impact. The closer your hands are to your body at impact, the more you can be turned on the ball with the shaft returning to the original hand plane as an ideal. This is essentially what I've been aiming towards. One has to have a flat plane on the downswing to achieve this as a steeper plane leads to pulls/ slices, or early extension to get the clubhead back on the inside to avoid pulls/ slices.
My shoulder plane being flat and picking the club up in front of me makes me get to the top of the swing in a position where I need to drop the club back onto plane and this just isn't possible with my limited shoulder turn and quick transition.
I have been working on this for a very long time and it has been impossible to resolve. :-(
Cipher - I think you've picked up on the fact that above the waist I'm a low handicapper, nice arm position etc, but below the waist I'm a high handicapper, not sure if it's my pivot on the backswing or my transition move but I cannot get into the correct impact position described above.
Here's a swing from today, slow motion then a few at standard speed so you can see the rhythm, also it's a driver. In this swing I'm essentially allowing the club to set on the same plane as the shoulders, i.e. very flat. there is more forearm rotation to allow this and to be honest I was getting through the ball really nicely and a fuller shoulder turn than normal. I did then try steeping the shoulder turn (and allowing the club to set on the steeper path to match) but it just didn't work as well, probably because of the poor lower body action.
Thanks all for your comments/ help and taking an interest.