Hey! So I'm working on a commission for alto sax and piano. I had an idea of using two pianos: one upright piano with the practice pedal down and one standard grand. (The reason for this being I want to still have access to a lot of extended techniques you can do on a grand but really want that sound the upright with practice pedal has.) 

Anyway, one thought I had to differentiate which piano is being used was to use my aleatoric box notation tool I downloaded from Robert Puff's Of Note blog and put the music played on the upright inside the box. Unfortunately, since it's an expression it doesn't continue to the next system like a smart shape. My question is, is there a way to make an expression act like a smart shape and allow the box to continue to the next system unbroken?

My current solution is to have two piano staves, the upright smaller than the grand, and putting a note on the first page that the upright is set with the practice pedal throughout.