Replying to Line chronic sizing

thinking about snagging a pair of this years chronics but wasn't sure whether to go with 171 or 178. they would be my park ski- I ski mostly rails and not too many jumps, and when I am jumping its nothing too big, although I would like to work on that this year. I'm 5'8 and weigh about 135. for the past few years I've been skiing 171 thalls, which I love, but being pretty soft and also having the early rise I was thinking of sizing up to the 178s for the chronics. 171 size is great but I definitely don't want to go any shorter, how do you guys think the longer size would feel? the 178s are just barely taller than I am. thanks