I also find it impossible to get the large contoured on without padding and painful on my ribs.
I bought a cheap camping mat (£3) and cut out two squares about 2" bigger than the diameter of the domes and cut out a circle in the center about 2" smaller than the diameter (I can get the exact dimensions if you wish)
Because it's cheap it flexes and moulds itself like a second skin. It's 5mm thick to start but compresses so you only lose a couple of mill from the volume .
I tried the foam rings but they take too much from the volume and after a few weeks the domes slips down the inside of the ring.
I bought a cheap camping mat (£3) and cut out two squares about 2" bigger than the diameter of the domes and cut out a circle in the center about 2" smaller than the diameter (I can get the exact dimensions if you wish)
Because it's cheap it flexes and moulds itself like a second skin. It's 5mm thick to start but compresses so you only lose a couple of mill from the volume .
I tried the foam rings but they take too much from the volume and after a few weeks the domes slips down the inside of the ring.