An Essay on the Best Position for the Lady's Left Hand in a Ballroom-Hold Swing
I am using the traditonal terms of Man and Lady for the two dancers; please feel free to substitute Lark/Raven or any other terms that you prefer. And, of course, these are just role names; either gender can take either role if they so wish.
See here for details of how I teach a ballroom-hold swing.
I firmly believe that the best place for the lady's left hand is resting on the man's upper arm in a relaxed manner.
There are some very well-respected callers who teach a swing with the lady's left hand on the back of the man's shoulder blade. I believe that there are many challenges associated with this:
The man, who, on average, has longer arms, reaches under the lady's arm to very easily reach her shoulder-blade. The lady, with her (on average) shorter arms and probably starting from lower down, has to reach OVER the man's arm to get to his shoulder-blade. Yes, some ladies can reach. But in my experience many ladies cannot easily reach and still be comfortable.
If they can just reach, many ladies then, instead of just placing their hand on the man's shoulder-blade (so that when centrifugal force increases they can resist it) they actually press into the man's shoulder-blade. I am not sure if this is just bad technique, but I suspect it may be partially to do with the fact that they can only just reach so they press so that their hand doesn't slip. It can be quite uncomfortable for the man.
Even if the lady's arm is the same length as the man, and she is the same height, she still has to reach over his arm, so it automatically pulls you closer together than you need to be, and even closer if her arm is shorter. While there are fun swing variations where we get really, really close, in a standard buzz-step swing I donít believe that being forced closer together is desirable.
It is not necessary if the man's hand is well placed. Each person should support their own weight, so all the connection is doing is resisting centrifugal force and, in 50 years of swinging, I have never found that a problem. Of course, if the man has not placed his hand well, so that there is no connection, then the lady may feel forced to grip the man's arm, or try to reach around to his back, in order to to create some connection. Men, learn to place your hand well on the lady's shoulder-blade. Just connect; don't press.
It is quite common for the lady to twirl under the man's arm at the end of a swing. If the lady twirls counter-clockwise that is not a problem. But if she twirls clockwise then she will break her arm. Probably not a problem if the lady is completely in control of the twirl - she just prepares for it by moving her arm, but if the man takes some part in initiating the twirl (which I believe is very common) then if he tries to twirl her and she reacts slowly, then either the twirl fails or she gets hurt. Of course if the lady's left hand is just resting on the man's upper arm she can twirl either way without a problem. The hand just slides off easily.
In complex flourishes, such as a Texas Tommy/Apache Whip exit from a swing, then you really do need some lead and follow, and it is nearly always the man leading the lady. A move like that is impossible if the lady's left hand is on the man's back. Believe me I have tried it!
Yes, there are some skilled dancers, with fast reactions and long arms, who can successfully place their hand on the man's back and still meet all these challenges, but for the vast majority of dancers this is not necessarily true.
I hope that helps you understand why I always teach the lady to leave her relaxed left arm resting on the man's upper arm. :-)