I've had the car for about 5 days now. I will say it took me a better part of an hour to get the seats adjusted for my height. (I'm about 5' 7") I'm short, but I found that raising the seat height and keeping the back pretty straight (none of that lean-back high school driving) is the most comfortable/best driving position in this car. It was awkward at first but I really think an "upright" position feels, well.... right. At least for me. Just don't make it too upright, or you are eating the steering wheel
I also think the seats are pretty supportive in the lumbar region but as far as the thighs go, there is a little to be desired. Maybe try adjusting the seat so that when your foot is on the dead pedal, your knee is still slightly bent. Works for me but I should also note that this is my first MT sports car so
If all else fails, maybe go the aftermarket route and look for a seat that fits you better.