I have a Shires alto and I'm using an Elliott C cup. I have a C2S alto shank which goes into the lead pipe further than normal, and which seems to work ok. But I'm wondering if the c2 alto with regular shank would be better. it would have the advantage of lining up 1st position more like my other horns, but I'm wondering if the relations ship of the partials to each other would be affected. Thank you

The alto backbore is very different from the #2, and yes it lines up the partials better. I generally still recommend the s (smaller) shank.

I found the alto S works better on shires. The slide on those is already too long. But trying to get the system as short as I want means the bell position gets worse and worse.

In any case, the alto s makes it play beautifully.