Hi alpharalpha,
My answer here would be the same as I’ve provided to you in the past where it wouldn’t be possible for me to tell what might be comfortable to you in a custom mattress that you’re making for yourself. Even foam experts in the mattress industry are often surprised at what a mattress feels like in “real life” versus their theoretical design, and many of them have performed this for a living for decades.
I’m guessing you mean an ILD/IFD of 34 or 44. I know you were trying to approximate the feel in a couch cushion you’ve slept on before, and to assist you in that endeavor, the Polyurethane Foam Association lists common IFD of a mattress polyfoam core and firmer seat cushions in the 30-36 range, and firm mattress cores and thin seat cushions in the 36-45 range.
If you are considering ordering from Foambymail (AKA FBM or Foam Factory and other names as well) then I would read this post and this post and this topic (about their polyfoam and sources) and this post (presumably from a past employee) before buying anything or considering them as a reliable supplier that provides accurate information about their foam products.
I would consider foamonline to be a reliable supplier and they are included as one of the better online options for polyfoam I’m aware of in the component post here .
Phoenix