Side Lying Trunk & Leg Raises

In my currecnt abdominal training I have been doing “Side lying trunk & leg raises”. @ 1st I struggled to do more then 4 on each side to the count of 5 second holds. I’ve since reached my goal of doing doing 10 reps. on each side for 5 second holds.

I’m looking for the next level. Or variation for this execerise. Or options out there for exercises that involve lateral flexion similiar to the above.
Aside from manipulting the tempo, example: 10 second holds or 313 etc… I would like to hear from some of you for other options available.

Stage II on the GBII book (page203) describes a progression of the above to “Side raises on roman chair”. My gym does not have a roman chair. And I have read that I could place 2 benches parallel to each other, hook my feet under 1 bench and lay on my side with my hips on the other bench and do my lateral flexion this way ( Or use a swiss ball ). My gym does not have many extra flat benches or swiss balls laying around. Many are in use all of the time.

Does anyone have any other suggestions on lateral flexion exercises?

Today instead of doing my “Side lying trunk and leg raises” on the ground. I did them on the hip/thigh(lower back) extension device. I did notice the seat would not adjust to the height I needed for hip support, and when doing them felt it was not targeting the muscles enough.

My progression is coming along nicely.