Hi Clawdia,
I would call and ask them about this. I was curious so I called CozyPure and talked to Hans and asked if they’d had any other comments about the protector not fitting or fitting too tightly (which would affect the feel if there was no more stretch left and it was creeating a “drum” effect on your mattress). He told me that he hadn’t heard this before and most of their mattresses are the same thickness as yours or in some cases more and they work well on their mattresses so he suggested you call them to find out what may be happening. It seems odd to me because your experience is different from another member that purchased it here (with pictures) which appears to show that with the one they purchased there’s lots of room.
Phoenix