Balcony Growing: Can I/should I control vegetative growth by trimming?

Hello and thanks for all of the information I've learned from these forums prior to registering just now. I'm waiting for seeds to arrive and I want to feel as prepared as possible for whatever problems might present themselves in this plan for my 1st grow. Here are my questions which I have not found any answers to despite keyword searches. I am eternally grateful in advance for whatever guidance you can provide:

I will be using a "super soil" method and rather than growing completely outdoors under full sun all day, the plants will be in 3 gallon containers and moved between 2 outdoor balconies in my apartment. This will afford them a good 6-8 hours of direct sunlight daily. I've read so many warnings about plants getting too leggy and stuck in vegetative growth unless they get considerably more sun than this, so I'm concerned (or maybe this is more of a concern with indoor growers?). Either way, I really do not want them to get taller than about 3-4 feet because of, well, cops. I prevent my basil from getting too leggy by pinching off the the top leaves in the early and mid growth stages. Is there an acceptable way to do this with marijuana so the plant broadens rather than heightens?

Also considering my growing plan above, is there a way to force the plant to go into flower once it reaches 3 feet? Since I'm using a water-only super soil method, my plan was not to change NPK ratios for the different growth stages.

As a final FYI, the seeds are sativa dominant (which I know grow taller) and I live in a tropical climate.

Thank you, thank you, thank you!

The super soil recipe calls for a minimum 7 gallon container.
For stealth grows I like to use fast flowering strains, particularly indicas. They are shorter and you break the law for a fewer number of days. You can force flowering by putting black garbage bags over them every day for a 12/12 cycle. Or you can throw 'em in a dark closet in the house. Pain in the butt, but low tech.
You can search for topping or LST. You can top weed, but not the way you do with basil. You need to do it lower and have an overall strategy of plant shape and size. You can top it above the four lowest branches and then tie those branches down.

Your plan is achievable, but you need a little more knowledge. I recommend the Jorge Cervantes book as a good basic, but thorough, overview of pot growing.

Good luck.

Thank you very much, kamut. Great guidance and advice all around. I wish I had known the terms "topping" and "LST" which would have made my keyword searches more productive. I chose sativa seeds for the high I prefer, but that's valuable to know about indica. I will also check out the Cervantes book. Cheers!

Indicas are best for a discreet grow but you can LST a sativa and keep your plants quite low. Tie her down gently now (it's not too late!) and a little more every few days. Train her into a circle or an S around your pot. When the branches come up, tie them or use a screen (SCROG method). Much better than topping, IMO