Thanks for the reply Blue.

I've found some chains can be forgiving. I ran a KMC 9 and Campagnolo 9 on a Shimano 8, the former giving the slightest degradation, maybe one balky shift/ride the latter with no real problem. My current project, KMC 10 on S9 isn't as reliable, but that's my campy/shimano mix so many more variables. Also, the 9-10 difference is bigger than the 8-9 difference. I'd assume downshifts would be where narrower chains would suffer, and my worst shift is actually my 2-3, which has narrower than stock spacing. And while that custom spacing, 2.29mm, is only .25mm narrower than stock S9, and my KMC10 chain is a whopping .72mm narrower than the intended S9 chain, the upper gears shift fine with 2.54mm spacing.

Perhaps it's my wariness of mauling (I tend to be careless) the insides of an expensive Campy shifter, but I feel like arithmetic can still carry the day. I did the above respacing with the assumption that as you said derailleur ratio is "non-linear ... for all brands of derailleurs". It must be if cable pull varies and spacing is constant (in the Shimano case).

Your Tiagra 1.4 find was golden. I've read that site about 62000 times and still missed that. They kind bury it but that's no excuse. My concern remains that the Campy and Shimano non-linearity don't match, as your cable pull graph clearly shows, so custom spacing would still be theoretically needed.

Given that it's a simple calculation (which I haven't done cause I'm too busy talking about it) to figure out the Shimano derailleur ratio graph from your valuable cable pull measurements. I half-assed this: inferring the non-linearity differences from the difference between the Shimano and Campagnolo cable pulls. To do it right you'd use the graph/table of the derailleur ratio combined with the shifter cable pulls.

Again, this is a theortical ideal. It sounds like you've mated a 4700 to Veloces and it sings. That's really the end of the story.

My other project, Campy 9s Barcons (pre 2001), XT derailleur and S7 cassette isn't faring so well. It worked great with a newer Racing T derailleur (which broke) and S8. Maybe this is a 4700 candidate.