Check out blcktpgsr's recent post in his build thread. You "should" shoot the headlights in their halogen form against a wall, mark where the output lies with masking tape, and use that as a guideline for the projectors. However you need to make sure that the halogen headlights are adjusted EVENLY and CORRECTLY prior to marking them on the wall. I actually prefer to remove them from the vehicle and shoot the halogens in my basement after they have been removed from the adjustable mounting bracket, then mark accordingly on the wall wish masking tape.

I have a few other tricks up my sleeve for getting the alignment but I can't give away all of my secrets!!! haha

PS - TRS has a Retrofit Guide that can help you walk through the process.

GL!