Just to clear up any misconceptions, I don't make the ZIPP props. You'd have to ask Joe about that.
On a related issue, I use 6061-t6 for all the fins I make for Joe, including hydro, mono, rigger, etc. Different thickness for each type, but all 6061. It is rugged, takes a form fairly well and doesn't crack readily. Just don't put a sharp bend in them. 5052 is somewhat softer and a lot more difficult to machine to a nice finish, in my opinion. 7075 is a lot stronger than most other alloys, but quite a bit more expensive. With its higher silicon content, it is also harder on the tooling.
Fred