Dit mattress comfort later suggestions

I have a TPS 15.5g quad coil support layer zipped up in a 9 inch Brentwood home cover. For comfort layers, I tried 2 inches of soft serene foam and 3 inches soft talalay latex. This was too soft and caused back pain regardless of which layer was on top. Last night I removed the Serene foam and used just the latex. This was too firm and my shoulders went to sleep all night. Open to suggestions, tia!