PRECES AND RESPONES

Hi, I am currently writing a set of ATB preces and responses for choral evensong and wondered if you could help.
I have managed to create these bars that are separate to the ATB parts for the priest to sing and wondered if there was a way to shorten the excess part of the bar. I've tried using horizontal frames, which worked for the first few responses as the cantor line is short, however it does not work for the 'glory be to the father...' line as it Is too long. Is there an easy way to solve this?

I have attached a photo of the page.