Alright so I am 5'8 and I ride 161 salomon threats center mounted. I am supposed to grow over the summer and I am planning on getting invaders cheap now that it is the end of the season. I was going to get 171 instead of 178 for sure but then I did some measurements with a measuring tape. Getting 178 and adding 17 centimeters to my 161 park ski is only 6.7 inches. Invaders are center mounted so that is only 3.35 inches more on each side of the ski. 3.35 inches on each side is nothing and the difference between 161 and 178 will not be noticed too much. Hope this helps others in the same situation.