Im 5 9 and 145 and ride 178 park skis and would not go shorter, if i was in your situation, i would buy 176, but since your converting, a 170 should be good, but DO NOT go 160, that would be a really bad idea.
made'n's are definetley overkill for rthe park, too wide and heavy, be hard to throw around, i would definetly go stl if i weere you but even a fujative would be better then the made'n