The seat cushion on a coupe is different.
If I remember correctly, there's a T25 torx screw at each end of the seat, facing the front of the car, then the thing will just lift out, but there are tabs or clips. I'm not exactly sure what to call them, but just give the seat cushion a few firm upward tugs and it should come out.
But as far as taking the rear seat out, why? So you save a couple of pounds? In all honesty the little amount of weight you're losing won't be enough to make any real change in acceleration. Any sort of change it does make will simply make the weight balance even more uneven, and since these cars are pretty nose heavy already, you'd really just be hurting the overall performance.