Shop lights or fluorescent lights in general are minimal for a light source and will need to be kept about 2 inches above the seedlings. I don't see a problem with light loss in such a small space. Al

Use one of the reflective emergency blankets you can often find in the camping section of sporting goods stores.

I had just posted some pictures of my set-up in a related thread below (use the link below to view it). This uses the reflective foam board insulation, as I wanted the double-bonus of hopefully containing a little more heat from the bulbs. (And according to the helpful people on this forum, they don't believe it will go up in flames, LOL)

Here is a link that might be useful: Forum Link