I'm also using 18/6. I have a cheap timer just to make sure that I stay on track, which is really useless because I'm checking on them every few hours or so.
I'm heating up now, that was my 100th post, yay me ...lol
I sent my t5's back to the manufacture as they were tripping my breaker, I'm using 6 cfl's now . 4 6500 and 2 2700 that seem to be doing great. youtube "diy cfl grow lights" and you can find some cheap and effective grow light ideas.
I'm going to place an order with Judy for more chocolate habs when she gets a new shipment in. She is currently out of them right now. My caribbean Habs are growing like crazy..
I would use conduit also. very sturdy. Not sure about the 3 way elbows. maybe reg pvc elbows and epoxy them. Also wood dowels might be the way to go. Let us know what you decided to go with and post some pics. Good luck with it...