Just as an update. I've been working less on the deltoids, but walking a lot more (probably 36 holes or so a week, 9 at a time, occasionally 18 ).
Building a little upper body strength and stretching has lead to more of a turn of the upper body against a firm lower body (ie the X factor) than I was capable of before. This has just started to sink in, physically, though. The result is that I am exhausted after hitting not so many balls, as I am using muscles in the upper body I have not used before. What happens when I develop more co-ordination, and maybe some smoothness, who knows? But I'm optomistic.