We use primarily SB pockets with CB inserts and love them!
Are your inserts soaked when you have leaks? Maybe you need more absorbency (in which case I don't think SB inserts would help)
If not, do you think your fleece is repelling?
Or does your babe pee really fast? (I notice that if I use hemp without any MF on top, I get leaks because the hemp can't absorb fast enough)
Are the leg casings causing wicking onto clothes? (Dd doesn't wear onsies because of this.)