I totally forgot that side crunches on the Swiss ball were an option! (This is what comes of not having the book to consult.) I would have much preferred the side crunches, even with making the Hanna flexion harder by holding a weight behind my head, because balance makes for more muscle work.

Though thanks to my NRoLfA reading, I've been doing side planks lately, and if I'm feeling masochistic, which I usually am, try for the side plank version where you lift a leg up. These have yet to bore me, but that's mostly because I can only hold that for 30 seconds at a time, and that's if I'm lucky.

I really enjoyed stage 5! It was like stage 3, except more intense and slightly shorter.