You have to pair them carefully. On the GS-1000, GS-1000i, and PS-1000 are the models that they were designed for. But, they work pretty well on the PS-500, too. In fact, I don't think I'll use the regular L-Cush on the PS-500s again. The G-Cush is just pretty impressive.
The downfall is that the pads can put pressure on the tops of your ears. The headband may have to be raised up a bit. I currently use a piece of 3/4" foam that I insert between my head and the headband to raise them slightly. Then, the pads don't rest on the tops of my ears.
Then again, we all have to realize we hear things differently. Not all pads will be all things to all people.