Hi kennyames,
If all 3 polyfoam layers are 1.5 lb polyfoam then you would have 3.25" of 1.5 lb polyfoam in the upper layers of the mattress. While this would be higher quality/density than you would find in many mainstream or major brand mattresses … as you can see in the guidelines here they are in a lower density range than I would be comfortable with in a one sided mattress (unless there was only about an inch or so).
Phoenix