I'm going to have to jump in here and say that you're making a mistake. Why you ask? Well, I happened to be reading the "optimal three pair quiver" thread and came across your post:
Originally Posted by Rise To The Top
Volkl Racetiger SL WC 165
Volkl AC4 163
Volkl Mantra 168
What jumps out at you here? ALL OF THESE SKIS ARE UNDER 170CM AND HAVE RADII IN THE TEENS!!!!!
Why the hell would you put yourself through the punnishment of skiing on a 187cm 27m radius ski if your ideal quiver has nothing even close to that in it? You clearly aren't comfortable on long skis, so why force yourself onto something that is going to be close to twice the radius of your ideal skis? Not only will you have to ski on these things, but you will have to ski a tight course on them - with the hopes of actually being competitive. I don't mean to take the wind out of your sails but it just isn't going to happen because you still consider an ideal length and radius ski to be a 170cm ski with a sub 20m radius. There is nothing wrong with that, but I wouldn't try to kid yourself into thinking that you are going to be successful (fast) on a 27m 187cm ski in a course.
Even I am cautious about going too long in a course due to my size (I ski 186's) and I outweigh you by 25lbs, and am much older, and probably a lot stronger than you are right now. My ideal free-ski is also a 184 with a 29m radius. Your build/size/strength could all change within a few seasons, but you should be buying the ski that is going to help you be fast now, not when you are a second year J1. By your coach saying that "you will grow into them" clearly shows that you aren't ready for the big ski yet... and makes me wonder why any coach would suggest that one of their athletes jump up to gear that is clearly beyond their current ability to handle. If I were your coach you'd be on the 185 without a doubt.