Replying to Some questions about ski length and binds

Hi to all. I have some questions and think your advices will help me. I want to buy a 2nd couple of skis for powder. I decided to buy Armada JJ's, but i don't sure what length to take: 185 or AK 195? My height is about 188cm, weight - 80kgs. I read that they shorter then they are, is it true? So i should take 195? And the second question is what binds to mount on them? I have Armada AR6 with Salomon 912ti and i like this binds. I read some information about Salomon STH14. What can you say about them? Or maybe STH12? And some note: my father will ski on them sometimes too, but his weight is bigger than my (about 100kgs). Is it enough 12 DIN or better 14? The final question^ where to mount binds? On recommended line or +1-2cm forward? As i understood recommended line for just skiing, move forward for better skiing in switch and tricks? Thankx.