i would hang each one with a yo-yo hanger so you can raise them up. i'd think the bottom of each side led should be the height of the top of the pot.
and if the plant does happen to stretch, you can move the lights up too
i would do 12 with a really short veg time in 1 gallon pots. that's just me personally. when they get about 2 weeks from finish, start vegging new ones.