Uncle_Bob, Yes, that's why I raised that question and that's exactly what happened last night when I put extra pillows under the mattress to experiment,not by very much. Mike's chin did tend to drop down and I heard a lot of snoring during the night which woke me, so I pulled the pillows out, he raised his head position and the snoring stopped. His report showed that during that snoring phase he leaked more and his pressure hit the max (13cms)that whole time(about 2hrs). Afterwards, he slept at 11cms the rest of the night with good leak line. The cardiologist didn't really insist on raising the mattress as a health issue, he just mentioned it in passing so I'll leave well enough alone. Thanks.