Wirelessly posted (BlackBerry8530/5.0.0.1030 Profile/MIDP-2.1 Configuration/CLDC-1.1 VendorID/417)
Rules regarding stopovers, open jaws, fuel surcharges, etc., will vary widely depending on whose miles you will be redeeming. AA and BA both permit one-way redemptions on CX, so there will be no issue about having an open jaw. BA charges for each flight segment flown, so you will pay separately for the JFK-HKG, and the HKG-PVG flight, regardless of whether you stop over or merely connect in HKG. AA will not permit a stopover in HKG on a JFK-PVG award.