Originally Posted by gfk_velo

In essence, for each >6.25 but less than 12.5mm increase in chainstay length, you need a male-female pair of links because although 1 male-female pair is 1" (25.4mm) long, you can't fit a half-link ... unfortunately, we aren't working with BMX / Track chain ...

The exact amounts of the excess that get used are slightly variable because of chainring and sprocket sizes plus the angle of the chainstay relative to the BB shell - all of that disturbs the triangles that the chain, in each case, forms the long side of. But in general the sum given holds good.

There are one or two UK OEMs that Campagnolo deal with, with long chainstays ... Moulton for example ... I will check with them what is supplied by way of chain (the factory are now closed until January). If they're supplied longer-cropped chains, we can probably sort out Campagnolo chain, rather than the KMC chain which voids warranty.