They're almost always "old enough" There are some people that flower from the very beginning, so yes they're old enough. I'm only on my first grow, but I let mine get nice big over 2 months before flowering. That's for my first grow though. I may actually do a bit less time. I think most people let them go for a month, but it depends on what you want. If you have the room, then let them veg longer because you will get more out of them. If those are in little cups though I would definitely replant into something bigger before flowering.
16oz still aren't big enough IMO. You don't want to get part way through flowering and have the roots bound up.
He is right. You need at least a 2.5 gal. The roots will suffacate each other. If you dont change them quick stunting of growth with begin. Also you can flower anythime. Hell I grow some my plants on 12/12 from seed. but like the others said lil longer veg wont hurt to ensure you yeild suitable amounts. Hope I help,
Yeah I would flower now for sure considering the space that your working with, as long as you flower long enough and don't let your cravings get the best of you, you should right on point