I have to agree that the 777 seat is a bit of a punish. When I queried why it is so damned hard when I first went on to it, I was told it is the first cockpit seat built to new 16G specs.
I find the 16G comment believable - it would take 16Gs to make an impression on the bloody thing.
I have discovered through trial and error that the comments others have made before me do help somewhat - high setting of back rest and elevate the thigh support so as to take a bit of the weight off the long-suffering butt bones.