Hi there
I've enjoyed reading your post so far, the uber-stealth grow ops are really fun for me to read about. Plus I'm intrigued by LED grows, you've got a double-point interesting grow!
The one thing that I would really focus on, it's been mentioned and linked to by Version 2, is some sort of carbon filter. As your plants continue to grow, they're ganna start smelling. This is ganna be a big enemy for you. I'm sure you're already working on this and planning it out, just something I wanted to mention again
Also, if you can rig together even a couple small 80mm PC fans for the ventilation/carbon scrubber, the air motion will help strengthen the stems up too, acting like the wind in nature and all.
Again, this has been a fun grow for me to watch, keep up the stealth and pure LED action! I'm looking forward to seeing how it turns out for you, best of luck!
EDIT: Just remembered, in addition to hydro stores, are there any nurseries or garden centers in your area? Sometimes these places are more likely to keep their soil indoors, greatly lessening the chance that you'll buy soil with bugs and stuff already in it. Check your yellow pages, hopefully there's a store like this around