Things that helped my application - became a HK Permanent Resident, so most travel originating HKG or nearby.
Track record of previous and future CX/KA travels
Sent in by email
a) Scans of boarding passes of recent CX/KA flights
b) Statement of activity from BAEC (last 12 months)
c) e-ticket of upcoming CX flights
d) photo of BAEC Silver Card
Whole process took one week from my first email to receiving the offer of MPC Silver, very efficient.
on November 5, 2018