Here is the quote right from the write-up:
According to the DOT (Department of Transportation) and SAE (Society of Automobile Engineers) standards, here are the requirements for headlight aiming.
The SAE specifies that if the optical center of the headlamp, or optical center height (OCH), is less than 90 cm (36 inches) above the roadway surface, then the reference point should be at the same height as the optical center. If the optical center is more than 90 cm (36 inches) above the roadway surface, the reference point should be 5 cm (2 inches) below the headlamp optical center. These reference points were adjusted for the greater alignment distance.
So I aimed mine 1-2" below the headlight height.
I think the reason why people end up having to aim their HID lamps so low is that they're too damn bright in a halogen projector, or they're prone to scatter. This is why I wasn't too keen on getting HIDs. Sure they're bright, but you risk blinding incoming traffic. Or, you have to aim them SUPER low and then reduce your range- so what's the point?
The LEDs are brighter than stock but not as offensive as HIDs. That's why I aimed them as Toyota and DOT recommends.