Shorter stem AND pushing the saddle back?
Making the effective seat-tube angle slacker making the BB further forward?
Sounds like it's the legs that would have benefitted and not the arms?
I'm not absolutely sure that it was better yesterday. Yes, my arms weren't aching, but the ride was hard and hilly and twice we had to walk. Now I've sorted the angle adjusting system out on Moulton, I'll be putting the saddle back in the long-standing position but tilting it up at the nose .......... and do a particular 18mile ride I know well.
Then, do it again (a day or so later) with Mercian as it always has been.
Maybe then I'll have some evidence of the way ahead for me ......... tilting or moving backwards.