Fixed Package Amends

Hi all,

Hope you're doing well. 
Just asking - not even sure it's possible - but are you able to add additional performances into existing Fixed Packages that already have sales on them? We've got a Festival that want to add an additional performance in of which we're selling passes via fixed packages. I think potentially not and we will have to setup another package and end the current one but just wondering if anyone has had any experience of this?

Thanks in advance :)

Ryan