Is this Kenneth at Cx City?
Affirm.
Are you talking over 100% of your salary, including housing? I'm on year 4 SO, and have a housing in excess of 65K, so my housing is more than 100% of salary, but the way they view it is 46k + 65k = 111k \ 2 = 55.5K. So if dealing with the HKMC, they normally will not allow a payment higher than 55.5K. Maybe there are some special circumstances that allow you to do so, but I don't know of any. If you are below 70% of value on your mortgage, then you can make it what you want, within reason.
My initial application was at the half-rate (still SO2), and was accepted. I later changed my payments to the full-rate when I became SO3, and the larger payment amount was accepted which is above your 50% formula. Maybe I got away with it that way, but I didn't even realize the limitation that the HKMC had. This was a 90% mortgage.
Good luck all!