Hillrider: I have not tried shiftmate and I understand they work perfectly but I wanted to avoid having buying something else and want a simple solution.

Elladaddy - I followed up this post with this :
https://www.bikeforums.net/bicycle-m...olution-2.html

I found if you play aroud with cassette spacing the shifting is sub-optimal as the chain width is designed for a specific cog spacing and increasing it will degrade shift quality.

The post above shows how to modify the cable pulley ( shown as the grey part 2nd to left in DaveSSS's post above) which is quite easy to access inside a campy lever. By shaving it down 0.5mm mm off its radius so it pulls less cable per shift it will mate with near perfect presicion to a Shimano 11 rear der and Shimano 10 spd cassette.

I run this setup on my Trek Emonda with Campy Veloce Ultrashift 10 pd levers and Durace 11spd rear der and 10 spd cassette to give a groupo that's cheap, reliable and as light as Durace.

Recently, I did a similar mod to some Veloce 9spd levers (ultra-shift) and ground down the cable wrap-pulley so it too pulls less cable per shift and mated it to Shimano 11spd rear der and Shimano 9sd cassette. It shifts really smooth and nice - like it's factory. However these are older style levers and to remove the cable wrap pulley requires a compete tear-down of the levers and the part is hardened metal so it is harder to file down rather than the plastic pulley on later gen levers. But with Shimano 9spd cassettes at $25 and a Tiagra der at $23 I don't have to pay the Campagnolo "tax" anymore so it may be worth doing if you have some old Campy 9spd levers lying around you are dying to re-use.

And just to follow up on DaveSSS's post, he (I assume he) correctly points out HOW campy makes the lever pull different cable amounts per shift - the jagged saw-tooth ratchet (shown in his photo) has different spacing between each indent (and if you look carefully at his pic you can see this) so it pulls more cable with each shift. I stand by my original assertion that the cable pull increases with each shift so it matches the arc of a rear derailleur which is non-linear -and this is true for all brands of derailleurs.

Unfortunately I hoped the original post would spark some more comments from others who have a curiosity about the geometry of deraillleurs (which are essentilly 4-bar linkages) as there is a lot of mis-information out there that needs clarifying.