Lower back mobility

I'm currently doing middle split and front split series.  

I have real bad anterior pelvic tilt and subsequent tight hip flexors and lower back.  

My hip flexors are getting worked in FS and is a work in progress. 

My lower back needs some stretches that I can do.   

What are some of your favourite lower back mobility exercises and stretches? 

Jefferson curls! Beautiful things

Inverted pikes on the stall bars always stretch my lower back well. Ease into these as I have found them easy to overdo. 

Bent legs jefferson curl is a very good variation.