Yep, epi = bed. They're not going to want to place it and then have the risk of it falling or not working properly. Even with a low dose, I'd imagine it would be very difficult to hold yourself up on a stool.
This might seem an odd question, but do you have big boobs? I laboured/birthed on my hands and knees, leaning over a fit ball for support. I knelt on a foam mat so my knees weren't too sore, the only thing that was uncomfy about it was after the birth, my chest was a bit sore from leaning on the fit ball for so long and smooshing my boobs into my chest.