transplant before switch ?

You want at least 5 days between transplant and flip to 12/12... how long you go is more about how large you need the plants to be. 3-4L per month of growing... so if you will be pushing 4 months, 15L is about right and 20L wouldn't hurt either... biggest difference is later on you might get an extra day between irrigations by comparison. the plant should at least double in size, so when roughly 2/3rds of L x W of intended garden size is reached, it should fill in well. can always prune a bit if it overgrows and is at risk of microbial issues from all the congestion.