Mattress Forum

This is a great forum and an excellent source of information.  I'm hoping to get some tips for softening up my too-firm bed.

A month ago, I was sleeping on a 4" memory foam topper over an innerspring mattress w/box spring.  The mattress was in decent shape (~15 years old), but the topper (~10 years) was getting a bit soft in the middle.  This was still comfortable, but since I also wanted to lower the profile of the bed, I decided to start fresh:

What I got:
Replaced the box spring with a 2" bunkie board
Replaced the innerspring with 4" Lux HQ from FBM
Replaced the old topper with 4" 5.3 memory foam from Foamorder

Although I knew the above setup would be firmer than what I had before, I think it's just a bit TOO firm to suit me.  I am a 150 lb side sleeper, and never felt the "bottoming out" when I had MF over an innerspring, but I'm definitely feeling it in my shoulders and hips through the MF over the Lux.

I experimented by putting my OLD topper under the new MF topper.  This was quite comfortable, so I think this tells me I need "something"more" between my MF topper and my Lux base, right?  (Note:  Using my old topper as a middle layer is not a permanent option, because it's much smaller than the foam on the top and the bottom.)

So here is my question:  What would be the best material to put between 4" of 5.3 lb MF and 4" of 50 ILD Lux that will:
     1) eliminate the pressure points from bottoming out,
     2) without significantly raising the profile of the bed?

Would 1" of latex help?  I am thinking of trying one (or maybe two) from philmoresupply.  However, if I have to add more than 2" of height, I may want to start over with a different base.  I want to keep the MF as the top layer. 

Thank you for any advice you may have!