Soft pads are great, until they bottom out. Ouchhhhhh... Have found a couple rifles that went from grins to ouch with a bit more powder.
A friend of mine put a mushy pad on his .470 NE. It was so soft that it came with a little stubby golf tee peg like thing that could be inserted into the pad so the rifle could be placed on the floor butt down without the pad squirting out from under the rifle.
After shooting it like that a few times he went a different route with a firmer pad.