Shortly after buying my car I had the driver's pad replaced. The seats are made of so called horse's hair - a spun plastic product that's pretty stiff and fairly thick. Perhaps you could have an upholstery shop (one that specializes in Benz' is strongly recommended) remove the bottom inch or so of the seat pad. The Benz seat pads are so stiff you'd probably never miss it. And if it doesn't work it's only about $130 for a new seat pad.

Cheers
…tracy