1) Ask your instructors, they are the only people who have seen you fly.
2) You being roughly 250 out the door you shouldn't be on anything smaller than a 210 and thats pushing it.
When you switch to a ZP canopy you do not want to do it while also downsizing. I am your size and my instructors told me to get something in the 210-230 size. That's what I did and it has worked out well.