pa42,
Boy you hit the nail on the head. I can't tell you how many times I have had to try and talk people out of filling up the tanks and reducing payload. Often a "study" of two aircraft starts off with full tanks, even though one aircraft has 100 nm more range in that condition. Or the "study" has both aircraft carry 2 hours of fuel, even though one goes 60 nm farther in that 2 hours.
I must say, we build aircraft to sell, so if the market wants longer range, more tankage or the rotor on the bottom, we will do it.