Change staff size for one stave

[Kalvin_gn]

Hi guys, i want to change the staff size but only for one stave like this :

is it possible or not ?

[dspreadbury]

Both of the staves in your picture look the same size to me. The little prefatory staff looks fractionally smaller, and I can’t think of a good way to do that in Dorico without a lot of trickery.