looks like you did a great job on your mod =)
about the resistors, a couple of things you can do, but a few in series, this will lower the total resistance and also the total heat, or put a few in parallel, that will divide the heat equally between all of the resitstors.

I used 4 1 ohm resistors in series in my PSU to get around 12.2 with about 1A load, or right around 12v with a 10A load.

the formula for figuring out heat on this circuit is 26.5 divided by resistance, so if you use 1 ohm, then you will wind up with 26.5w of power dissapation, which will burn out the 10w resistor, 2 will give you around 13.25w of power which will also burn out the resistor, 4 will give you 6.625v or about half what the resistor is rated for, which if sunk to the side of the case will give you a pretty good temp range of about 100F