UKH

Currently running a 25T with a 10 speed Veloce and wish to increase the last sprocket to make climbs easier. Reading some of the posters here I know that they run a 32T sprocket from an 11 speed Miche Primato on their 10 Speed.

Reading about it the Primato is made of individual sprockets so does anyone know what the differences (if any) are between a Miche Primato 10 speed and an 11 Speed, apart from the extra sprocket. Because my thinking is if they are the same then I can just omit one of the sprockets from a 11 speed. Anyone have any experience/views?

I don’t think it would work, but I think someone else would explain better why (if I’m right). I suspect the chain width would be different for one. 

And going from 25 to 32 might need a change of derailleur if the cage isn’t long enough. 

Campag do a 29t 10 speed cassette. That with a CT chainset saw me OK for everything in the Alps and Pyrenees and I'm pretty weak. I think mine is Record, but it's so long since I bought it I can't remember. I'm pretty sure there was a Centaur one which hasn't got a ridiculous price. You should be able to get one somewhere.

There is a 1/10th mm difference in sprocket width and probably a difference in the spacers too, hence while you many get away with swapping out one sprocket, using 10 of the 11 will add up to incompatible… 

https://www.sheldonbrown.com/cribsheet-spacing.html

The other slightly odd thing you can do if you absolutely must have 32t is match up your 10 speed Campag ergo shifter to a Shimano 9 speed rear mech and cassette. There is a simple way to make it work, I've run this with a 9 speed XT rear mech and 34t cassette for years on touring bikes and crossers/gravels without any issues. It does mean you will have to change your freehub body, all of which may or may not be worth it

Moving to a 29t cassette will make a huge difference though, I normally ran a 25t but the vast bulk of my cycling was hilly/mountainous and like you I felt I needed a lower ratio so swapped to 29.

I take it you have ascertained that your mech is long enough?