Elise Bacon - I love that explanation! Makes sense.... thank you! Glad the info is useful. It came up again just two days ago: I was teaching a client who had just moved here, had done pilates elsewhere and had assumed her "core" was still too weak to sit up straight. When I elevated her on a moon box for arm work, all of a sudden she could sit up and her abs kicked in and more to the point, she was delighted. It really does make a difference....
Susanna H I am noticing that it looks like I never replied to your comments/questions, and now I can't remember if I did or not... so here is an answer WAY past it's due date! So sorry! The padding that was used was what the upholsterer had leftover from another job, I don't really know what it was - but definitely not something you can buy in a fabric store, not just pillow padding. It's harder than Gratz reformer padding, if that gives you any information. Quite firm, more like how the reformer boxes are padded.
Susanna H 4 year late reply to this question - so very sorry again!! I feel that when feet/legs dangle, there is a very subtle gripping/holding pattern that happens in the low back/sacrum because the weight of the legs/feet create a drag on the pelvis. Often not noticeable, until you ground the feet on something solid. So when there is a situation where there is nothing to put under the feet (or I'm too lazy to go get a box, LOL!) I have the person activate their legs by flexing their feet and "hugging" with their heels... if this makes sense. So their legs are not just hanging.