My Hawk's foam mattress has always been pretty firm ( to say the least ). I put a 1" memory foam topper on a few years ago, but it was still hard as a rock.
So I finally decided to do something about it;
I checked out various options but decided I didn't want to spend any money, or waste the foam I already had. I figured I'd try this out, and if it didn't work I'd pursue another solution, with only my time wasted.
I made a core drill out of 3/4" emt with a 1/2 bolt pushed in it. I sharpened the inside edge of the business end and got to work. I drilled a series of holes on 2" centers, concentrating on the areas where my shoulders, mid-section, and hips would lay.
The holes provided a bit of cushion, but the real difference was made by slicing halfway thru the foam in between the drilled holes. This allowed the individual foam columns to act like springs and conform to my body much easier.
I tried it out for a few nights and gotta say I am very happy with the results. It's like having a new bed, I can't believe I didn't do this sooner.
I thought the holes might reduce the insulation of the mattress, but have not noticed any issue yet. I did keep the cores I drilled out ( figuring I could cut them to 1" long pieces and plug the bottom of the mattress if needed ) but don't think that will be necessary.
Will follow up with a long term report once I get some more time in the saddle.