Assume you want those six darlings to fill the whole space nice and evenly? There are many ways to train and I am no expert, but, it helps to remember that the plant puts the most resources into the highest parts. Whichever branches/tips are the highest - will develop faster than the rest.
Tipping the plants will encourage branching, so tip away when it is time and keep things as level as you can. Control of the total size of the plant (assuming photo) is achieved by how large you let it get when in veg before you change the light cycle to 12/12.
If these were in my garden they would have at least another 2 weeks of veg to go before tipping. I'm a late tipper though according to my mates lol. :) It's all good a bit of trial and error and you will be all over it.. Happy days.