I would use a flor on the seedling..... at least for a week... you can get one cheap at a hardware store... couple dollars....
Many a young plant have died at the hands of a HPS.... After your seedling is 1-2 weeks old turn that HPS on..
I 'd start withthe hps around 3 feet away... and then move it 1-3 inches closer to the plant every day .....
If you have glass on your reflector you can eventualy move the light to just an inch from your plants... just make sure you have a fan blowing DIRECTLY between your light and your plants....

good luck : )