I am 6ft 1 and almost 300LBs. I have no clearance problems in my 300sdl. the mileage is very good considering the cars enormous size and weight, 28mpg. I believe if I change the injectors I can do a little better. Obviously there are smaller MB diesels that are far better on fuel economy but for my size I am very happy. As far as the springy seats. I have read some threads about installing cheap pool noodles in the springs to firm it up. I have gotten used to the spring a little. It is nice on big bumps. What I really hate is my climate control. I wish I had simple buttons to control everything instead of the cc.