Aeropack Retainer

Greetings! My current project has a 75mm motor tube, and I’m going to use an Aeropack retainer. My question is: Since it doesn’t have an inner lip like the smaller retainers, do I mount it flush with the end of the motor tube or leave a small gap to allow for the motor’s thrust ring? Thanks, and see everyone at LDRS!

Chris Uffelman
TRA #10141 L2