I think it is way too soft as I wake up stiff as a board.

i don't think this mattress is suitable for me. I do have silent GERD but with the head up slightly I slip all the way down with my feet hanging off of the bottom. It doesn't seem to break at the right point. also, I am wondering if it is too soft, because I wake up stiff all over. I have noticed that it seems to sag around me in the middle...way too soft. I am mostly a side sleeper. But our son bought these beds for us; and apparently this was not discussed. I slept for a week on a hotel bed in NYC and did not have the gross morning stiffness. I am wondering if I can get a harder mattress. Can another brand be used with the current piping, etc.? It does nold the air pretty good. It came in a box literally destroyed and we could not even reach anyone to get any help. They brought in and said they were not allowed to set it up. We are 77 and 79 and needed some help but our son lives 400 miles away. What a waste of his money. But we dodn't want to hurt his feelings so I keep on suffering every morning. I even have trouble going to sleep on it. so I usually fall​ asleep in a recliner and then move to the bed.