Yes we have looked at those and tried a version of the more-full seatback type. The lumbar support type are the opposite problem. The G6 is quite firm in the lumbar and bottom half of the seat then is mushy and caves in in the upper half, thus no upper back and shoulder support. (The car also has adjustable lumbar and he has it all the way in.)

When I push on my GP GXP seat, the top half of the seat is quite firm and supportive. I then push in on his G6 seat and the top mushes in but the bottom doesn't.

I drove the car this past weekend and noticed the seat is wrong. I was not terribly uncomfortable but I sure wouldn't want to drive on a long trip in it.