Mosfet Td(on) and Td (off) must be equal
It's fairly easy to manipulate the on and off switching times of a MOSFET independently.

First, get a repeatable setup, with a decent gate drive IC. A resistor between its output and the gate will control the switching time. It's common practice to put a few ohms to a few 10s of ohms here anyway to tidy up the interface. 

Now replace that resistor with a larger resistor, shunted by the small resistor in series with a diode. The diode and small resistor will control the switching time in one direction, the larger resistor will control the switching time in the other. Adjust the large resistor value until you achieve your times, you may need to reverse the diode if you can't achieve equality.