NegromancerI'm a really similar height and weight to you and I also had problem buttering and fully flexing my AR7's. I found the issue was not the stiffness of the ski but it was my boots. They were to big so when I put all my pressure forward into the tongues of the boots my heel would lift a lot and so I would lose most of the pressure which meant it is hard to flex the ski properly.
I changed to a smaller stiffer pair of boots and it's helped a huge amount. I can now butter my AR7's pretty easily because my heel doesn't lift as much so I can apply way more pressure to the tips and tails of the ski.
Check and see if your boots fit properly before buying other skis. Also build muscle because of your scrawny and have no muscles you won't be able to butter no matter how soft the skis are.
Yeah that's exactly what I did, got a pair of three piece boots that helped a whole heap, can still nose butter lips rollers etc on my skis just looking for an all mountain playfull ski, so hearing that the rocker of the kartel helps a lot with being playfull I think I've found my ski, cheers !