I'm pretty much the same size as you, I went with a 171 cause I don't feel comfortable in the park on 181s at my size (I have tried, it's just really awkward, and I feel more at home in the mid 170s). That being said, read this and let them know that you want a 176 (by email...read the thread for instructions) and hopefully a 176 FR can be made...which would be awesome cause that's my favorite size park ski personally.
https://www.newschoolers.com/ns/forums/readthread/thread_id/617422/