FG,
did you get the option to take cash when you joined? Did you join in HKG or on a base? I thought only people who are on or were on a base could get the 15.5% as cash! Thats how i get mine as cash now.
If you are in the PF and want to resign after say 5 years, you would only be entitled to50% of the PF...the vested portion. If, on the other hand, you decided to take a basing after 5 years and then resigned a month later, you would have received 50% PF fully vested and the other 50% unvested, which means you have to pay HKG tax on the unvested 50%, so you would end up with 92% or so of your PF if you took a base first!