You need to veg the moms for long enough that you can take as many clones as you like, and often enough to maintain a SOG. This is why you should veg them for a month. If they grow faster, you may not need to veg for that long. You just need to figure out how many/how often you will need clones, and decide how many/how large mothers you need from there.
Then you can continually pull clones, let them root, transplant them and flower immediately in your SOG. By flowering them immediately, you will minimize the light you need to cover them. Even in SOG, however, a 150 is probably just enough for maybe 3x3 in 1G or 4x4 in tiny pots. That's stretching it bigtime.
I would grow them as large as you would like them based on the aforementioned figuring, and if they haven't shown sex, you can simply clone for sex. You can do this even earlier if you like. Just take a couple small cuttings from each of your plants and clone them as you would normally, but put them on 12/12. They'll show sex and then you'll know what's what. You can use these early clones to figure out your HPS setup before you take your first large batch of clones so you're ready to roll when that time comes.