Heavy - Those instructions were the ones I used On that site here they also tell you what resistors you need if you dont want to use light bulbs)

If you aren't getting enough volts on the 12v rail then you need to increase the load on the 5v rail.

This means using a lower ohm resistor or higher wattage light.

As an example, when I made my first ps I used a 5.8 ohm resistor on the 5v rail. This gave me 12.1v under no load but dropped to 11.86v under load when charging. In this case if you were to use a 5 or 4 ohm resistor then this would increase the voltage on the 12v rail.

On my newest version I used a 12v 50w halogen bulb on the 5v rail and now I get 12.2v without load and 12.05 under load