I recently took a six hour road trip in the EV6 for the first time. I had similar hip soreness. I bought a thin wedge pillow from Amazon to bring the tilt of the seat upright and that fixed the problem for me. https://www.amazon.com/gp/aw/d/B008GPR888?psc=1&ref=ppx_pop_mob_b_asin_title

It does make me a bit too tall (eyes are on level with the visor), but with the seat positioned as low as possible and slid back, I now find my pain problems are gone. It's especially helpful with HDA when I can sit like I'm in a normal chair.

Hope this helps. Hip pain is no fun