Way to change default length of song from "8 bars" to Automatic?

I bought a nice mic for recording band rehearsals and use it the first time last night with GarageBand on my iPhone. I really like having the db meter to adjust the mics gain. The only hassle is having to switch the recording length from the default 8 bars under "Section A". Is there a way to adjust the settings so the default is automatic?

I know GB is designed more for song creation and not recording - and if the simple Voice Memo app had a db meter, I would use that.

Any ideas?