Curling can be a sign of too much light, but in my experience the leaves normally curl downward and not up. It's usually accompanied with burn looking blotches too, so I dunno...moisture may be something to look at. Just a guess though.
So far as lighting goes, I think you'll find an exepriment done on the gardenweb forums by a member named macheske very interesting. He provides side by side progressive comparison of 24/7 vs 16/7 lighting with pics. It's a very interesting string of posts that provides updates all the way through actual outdoor harvests. From the experiment, one could conclude that the 24/7 plants exhibited marked advantages even after being transferred outdoors.
There's a load of pics on this link so it may take time to load, but I think the read is worth the wait:
http://forums.garden...9125925834.html
Thanks for reviving this information! That's what I'm going to do...24/7 till they go outside. Very, very interesting. I was just going to buy a timer tomorrow, but now I won't.