Thats a thread I'd love to take place in
I'm with tom - rotate your lights 90deg.
What are you using for venting? that fixture seem to me like a huge heat trap.
As for watering - I usualy cut a few small holes on the bottom of my cups to let water drain. you can heat a niddle and dig a few holes on each cup and help yourself not to overwater.
As for planting 2 plants in one pot - BAD IDEA. if one turns bad (male\hermi) you won't be able to take it off alone. plus, at a certain stage the plants will fight for space - which is never good.
if 2 plants pop in the same cup just pick one out and transplant it.
you seem to be spending a lot of time in your room so to help preventing overwatering I recommand adding some more perlite. the more perlite you have the better the drainage and the more frequent need of watering.
when transplanting to "normal" pots you could use less perlite as you should get the hang of things.
As for how many plants to use, first take into consideration that statisticly you will get less than 50% females. (as there are hermies too)
After the males and hermies got rid off you could fit how many plants you want.
small emount of plants will requier more veg time and topping is recomanded.
if a large emount of plants will be used you will need to work more while watering, cut on veg time and get more small plants.
my rule of thumb is to put the plants to flowering (12\12) light cicle when they fill the room horizonticaly.
oh, and about the lights your using - you could still use the CFL with no problems at all and save energy.
or use the HPS about 3-4 feet away from the seedlings. they don't need that much light. all that light just increase heat.
