When to Flower?

Hey guys, I have two 2 week old sprouts (they are about 3 inches), and I was wondering when to flower them based on my grow box.

BOX SPECS: right now im running 2 20 watt 6500k CFLs and 1 20 watt 2700k CFL. Once I flower I plan on using 3 or 4 20 watt 2700k CFLs.
Its about 16" by 28" height of about 30 or 34". Ventilation is good.

Also when should I put in my rack for LSTing my plants?

Any advice would be really helpful!

MVNugs

you have to realize that your plant is going to double or possibly triple in size from when you put them into flower.. so unless height isn't an issue for you, your going to have to take this into account for when you switch to flower.. personally, i don't have any height issuses, so i like to wait till i see one of two things, if not both, before i flower.. the first is preflowers, which i usually see at around four to six weeds from seed.. the second thing that i wait to see is alternating nodes, or branch sites.. as the plant matures and gets close to sexual maturity, it stops putting out its nodes evenly, and it will start to put them out no longer in pairs, one on either side of the main stem, but will put them out unevenly..
seeing one or both of these things will let you know that your plant is reaching sexual maturity and is getting ready to flower..

Yes, but Im worried height might be an issue. I hear of plants more than quadrupling in size during flowering, and sativas take between 50 and 90 days during flower to be ready to harvest (I hear).

Because my plants were rootlocked in solo cups, they are 3 inches and only have 4 true leaves (all to the top).

MVNugs