I'm about 165 lbs, 5'8". I tried the RX8 in 170, and found them good to go. I'm guessing that if I had weighd 223 lbs I would have found them lacking. If I were you I would try them in a longer length, and take them through some tight big bumps to see if they are short enough for you at the longer length.
In my limited experience, longer generally demands greater effort on precision from you (too demanding a ski is not as much fun) and may hamper you in higher speed mogul carving. Shorter means you could more easily overpower them, but you can have more fun because it's easier to let them rip. Choose the length thats the most fun for you. I would be surprised if you went over 180, as the turn radius also grows with length, and you seemed to like the radius of the 170.
ALSO ONLY A GUESS, but at 223 lbs you might want to check out something a little stiffer (6*? sx11? sl11?). I hope some of the heavier guys can better advise you.