When can I put seedlings under HID?

Hey guys and gals I have 4 seedlings that are about 3 inches tall and their 2nd set fan leaves are already in. My question is I have a 100watt MH that I would like to put them under. When can i do so without burning the babies up? Right now they are under 40 watts of T5 floros and just not growing as fast as I had hoped.

thoughts?

once they have 5 sets of leaves.

what, 5 sets of leaves? really?

I've seen skunk 1 and White Widow do great after being introduced to a 400w mh at 3 leaf nodes.

No hard fast rule. Some go almost immediately to 12/12 under HID's. Personally, I agree with the 4 or 5 sets idea at minimum if you aren't vegging under fluoros.

just my $.02 worth!!!