Dreamer Car High Back Support Used in a Car to Fix Posture

I'm actually using this cushion in my car. I know it's not meant for that, but it was the best solution I could find for an annoying problem that I can't believe there isn't a real solution for. I didn't need more cushioning for my back, but I wear my hair in a ponytail, and since my hair is kind of thick, it sticks out of the back of my head a few inches. The headrests in my car were apparently designed for people with no hair at all, so that the ponytail forces my head forward and makes it impossible to sit up straight. This problem has actually been going on for years without my realizing it; I just unconsciously started slouching and tilted the seat way back to compensate for it, but I recently started paying closer attention to how I was sitting in my car and realized what a big problem it was. I'm sure it's contributed to my poor posture and back pain. I don't want to change the way I put my hair up, because putting my ponytail higher or lower inevitably gives me a headache. The logical solution would be to change or adjust the headrest, but that, apparently, is impossible. I don't know if other cars make it this difficult, but in mine, it can only be moved slightly up and down (even moving it up as high as it will go, the gap between the top of the seat and the bottom of the headrest isn't high enough for my ponytail), not tilted, and can't even be removed. After much fruitless googling for options for changing the headrest itself, I realized I might be able to compensate for the stupidly designed headrest by simply moving the rest of my body forward, by putting a large, thick cushion on the back of the seat. Unfortunately all the cushions designed for cars I could find were just lumbar cushions, and wouldn't cover the whole back of the seat, therefore wouldn't actually move my body forward enough to solve the problem. This cushion is just barely long enough, and only just thick enough. I think it might actually work. I've only driven once with it on the seat, but I did notice a difference. The main drawback to this cushion is that the straps aren't nearly long enough. The top strap just barely can fasten around the top of the seat (it's under so much strain I'm not sure how long it will hold), but the bottom strap can't even touch. I realize this isn't actually designed for cars, but longer straps would make it possible for the cushion to be used in a wider variety of chairs. Fortunately it seems to stay in place pretty well with just the top strap. There also isn't as much lumbar support as I was hoping, but it's still an improvement considering my car has no lumbar support to speak of. For years I've been using a folded towel behind my lower back when I drive, but I think I can dispense with that now. And yes, I realize the headrests in cars are, in a perfect world, supposed to stay in contact with the back of your head in an attempt to prevent whiplash in an accident, but in reality you're moving your head constantly as you're driving (or you should be), and so it's unlikely to be in an ideal position anyway if you're unfortunate enough to be in an accident. I'll take my chances considering the alternative is poor posture and near constant back and neck pain. I just have to re-learn how to sit up straight in the car now.