I'm 6' 180lbs, and I've been on salomon 161's for the last year...almost everyone on here would say that they were extremely small for me. Despite that, I was able to spend my first year on twin tips landing medium sized jumps, skiing switch, and all mountain on any black trails.
Yes, 3 years on regular skis and 1 year on twin tips does make me a newbie when it comes to freestyle skis (and skiing in general), but if you're stuck with the size you have, it's not the end of the world...like the post above said, you'll get adjusted to these until you move on to the next size somewhere down the line, live and learn.
That being said, I recently moved to K2 PE 174's, though everyone said I should go 179 at a minimum. Sure, my next ski may be 185-189, but skiing a smaller ski isn't the end of the world...just use what you have and move forward as you see the need to.