Now I think would be the best time to start LST'ing. http://boards.cannabis.com/indoor-gr...ining-lst.html

Here is a nice post about LST'ing and when to do it. From the looks of your plants, now would be the best time because you only have about 3-4 internodes from what I can see on day 20. If you don't want to LST like the diagrams shown, you can always tie them back which is a form a LST, just a lil different.

Your plants look real good, I like the hps idea but only for flowering. hps on the top and cfl's on the bottom would be beautiful. Keep doin what your doin, find a nice water cycle that the plants like, start minimal on nutes to see how the plants react because you'll find that later on, one may not like full strength nutes, and one might. That how it was for me. One ate nutes like you wouldn't believe, and one was very sensitive. Best of luck, if you don't mind i'm gonna pull up a chair. My first grow is just about finished and i'd like to see how other people are doing to get ideas for my next grow to make it even better!!!:thumbsup:

edit: here's a pic of what I did of LST and then tying back one of my plants a few weeks into veg. hope this helps!!