Hi EnFuego,
You wouldn’t be expected to design the mattress from scratch, but all you’d be asking them is if they offered anything with higher density foam, 1.8 lb or above. That would be it.
You’d have to go visit the showroom in person and see if you liked the feel of a particular product. If you did find one that you liked and it used lower density foams than what you would prefer, you would ask if they could create a similar feel using higher density foams. Realize than any change in foam layers, even if the replacement foam is the same ILD, will result in a slight change in comfort. Your best source of guidance for any change in comfort with potential foam layer replacements will be the manufacturer, as they will have the most experience with their own products.
As you’re unable to visit Baton Rouge, besides the other business that I’ve already linked to in your area and my previous reply, your other option would be online and to use the experience and expertise of the members listed in post #21 here who are all very experienced and knowledgeable and specialize in providing the type of help and guidance on the phone that can help you make good choices. There are a wide range of latex and other options included in the choices there and I believe that all of them compete well with the best in the industry in terms of their quality, value, service, and transparency. I didn’t mention this previously as you stated that you were tired of purchasing beds sight unseen. The good thing is that the members of this site carry products using higher quality materials than what you recently purchased form US-Mattress.
I’m sorry to hear that, as there were a few Jamison mattresses listed on their site that might have been of interest to you.
Phoenix