Having given the GF a couple of road tests since fitting the new rods (and re-balancing crank to suit) I became aware that vibration was much improved to previously, insomuch as the bike was much smoother up to moderate revs. Nevertheless there was vibration, starting around 3,000 - 3,5000. Above a normal riding range, but irritating when giving it a handful through the gears.
And so I spent an hour or so this afternoon adjusting the balance factor upwards. Not road-tested it yet, but it seems smoother higher up whilst on the stand. Can add more if found necessary.
Update:
Took it for a ride today (Sun) - much improved. When I balanced the crank, I set it at c. 52% with the ability to raise to c. 62% in situ. Would estimate it's now around 56%.
Started the DOT too - first time I've kickstarted a bike since the new hip (only 200cc Villiers).