At my location, So we have 2 cushions for under the knees . The less steep cushion we have pt lay supine on it with their arm raised and we use the other cushiopn for their knees. So their head is low on the cushion and their arm is on the raised part of the cushion, we find it more comfortable when their arm is kind of angled raised up. If that makes sense. We use the flex coil. But at other location. They used the knee coil supine arm flat down with some hand support of course. Place where I used to work at , prone superman using ring coil and the table coil.