Oh, and just for fun I decided to clean and rebuild the light meter portion of the defunct multi-meter I had for gardening. Now it functions properly, as with disassembly I was able to find out what sort of panel was being used and what needed to be attached to it for the meter to work without that stupid switch and bulky crap. Turns out it just hooks directly to the meter, no caps or resistors.
Here's a pic of it in action, halfway into the canopy, with the HPS on with the T5HOs, and a pic of it in action with my thumb covering the panel - there's so much light, mainly from the HPS, that it goes through my thumb and still makes the panel give a reading.
Going by this meter, you don't want your light levels anywhere below 500. The outer seedlings are fine, the inner clones are going to kick serious butt.