178, especially if youre mounting at or near center, they will ride way shorter than the number on the topsheet says. im just over 6'0" and 186 on a camber/early rise center mount is like spot on for me. with that said, short skis are fun too. i rode 179 outsiders for a while which were stupid fun and hold up as long as you stay balanced. on the other end i have a friend whos about your height who's on 192 catamarans this lear lmao.
a lot of factors go into it, rockered skis typically you want to go long, super stiff skis you can go a little short. if you want a tighter radius, go short, if you like to go fast and straight go long