I fit in my old 996 C4 just fine as a daily driver for 3.5 years, and fit in my 996 Turbo just fine too; I'm 6'4 250+ and built big.

 

Has anyone heard of or tried moving the seat rails back an inch or so? Is it possible?

 

Tight headroom for 6'-4" plus drivers: I bought my car from such an animal. He specifically bought the car WITHOUT the power seats and gained 2" in headroom, or so he claims. He did fit in there adequately when I watched him driving the car before I bought it. I am not as tall so have no problems. The seats are standard manual slide with power back tilt.

 

I'm 6'4" and I fit in my 996 with no problem at all. I have the comfort seat option.

I have a friend who is 6'10" and drives a 996 turbo cab without issues. He usually has the top down, so maybe that's how he does it...