Every 3-7 driver board i touch I do this mod on anymore. If you can avoid burning off that much heat, go for it. I need to do some current testings, but i am guessing these saves quite a bit based on the amount of heat the stock setup puts out. Another tip.... When using the IRF9Z34N as the column driver, you can use about any weenie NPN transistor for the predriver, like 2n3904.
I have bulk quantity of IRF9Z34N at good prices.
http://nvram.weebly.com/transistors.html