I'm 6'2", 6'5 with my high heels on, and have no idea what I weigh (and probably don't want to) but I am no jockey and I've never had an issue with the adjusters. I also have a back injury and reckon that the D40 seats are some of the best seats I've ever had in a car, but aches and pains just like sitting positions will vary among all drivers so not every seat is going to be prefect for every driver.
I generally don't slide into my seat and I don't use the steps to climb into the ute but even climbing in I don't remember feeling anything digging into my legs. A mate of mine used to wear the right hand side of his seat down quite quickly because of the way he sat, he used to almost lean on the door pillar, we used to think it was because we were so often 4 up in the front of the ute but he did it when he was by himself too, it used to make the side of his seat sag before the middle, but I can't imagine driving the Nav like that.