Your yardstick is DTI, as you can manage the fluctuating EMI repayment of the home loan. If the DTI is less than 30 to 35 then you are surer to have the capacity to absorb the interest rate fluctuation of a floating interest rate loan.
An example to explain: If you earn Rs. 50000 p.m. and pay rs . 10000 as your car loan, rs 5000 for monthly bills and rs 5000 as miscellaneous expenses. This means your total monthly debt Rs. 20000/50000*100 = 40. Therefore, in this case opting for floating rate of interest will be at risk.