Adding foam to bed

We would like to add a foam pad under the double bed. It's about 3" of foam but could compress to about an inch. Question is whether we need to remove it to close up the camper. Have any of you done this? We have a 2016 Flagstaff popup with the heated mattresses.
We're wondering how much room is left in the space above the bed once the tenting is folded in, will the top close? Any experience out there on this?