Pretty sure that if you're dealing with the HKMC, you can't have a payment above 50% of income. I believe that if you are below a 70% loan, you can have a higher payment, with supporting evidence of your housing allowance, etc.
I didn't have that problem. 3rd year SO, so payments were over 100% of my income! I definitely had supporting documentation of Cathay's program, plus Kenneth at HSBC was a big help because he was familiar and probably knew exactly what HKMC was looking for.