I got to drive Niagara's '50 last year and it was a rather tight squeeze. I'm just under six feet and tip the scales at around 240. I recently got my '48 to the point where I could put the steering wheel in, and when I slid in behind the wheel, I was very pleasantly surprised.
Did I lose weight? Nope. The '48 has the tank under the bed instead of behind the seat, and I think I have about six inches more gut room.
