so I got twelve sprouted.
Training will likely be crucial to get that to all fit! Right now I have three (topped once and trained into a ring of 10 colas each) in a 4x4, and I can't imagine trying to squeeze a fourth in... there are, however, things you can do... All of which are likely to reduce your per-plant yield, but might help your overall yield.
Keeping them in smaller pots (i.e. 3gal instead of 5 or bigger) will keep the overall plant smaller.
Not topping or FIMing will keep them from going wide, but they will definitely go tall
Shorter veg cycle (make sure they're mature enough, healthy enough, strong enough, though... size along shouldn't determine when to flip)
Super-cropping and LST combined to make them grow narrow
In-short, you can make it work, but it will take effort and planning to avoid getting an overgrown jungle that's too much to manage.
Were it me, and expanding tent space or reducing seedling count was not an option, and I was faced with 12 viable seedlings heading into Veg... hmm... I guess I'd... top each plant twice (in a mainline config) to get four colas each, so I could keep them fairly narrow, still produce a decent yield, but not have them runaway from me vertically either. Then I would focus my training and defoliating to encourage staying narrow, and stay on-point with my light levels so they don't stretch more than necessary. Finally, I think I would probably go for a 3gal pot instead of my usual 5gal (as mentioned above).
Staying ahead of it, and planning what your next training/pruning/defoliation/etc. will be and is supposed to accomplish will help. I use those as a tool to make the plant grow in the direction I want it to. Whatever you decide (cull the herd, or go for it and how), keep us posted, and good luck!
