They don't need much light to stay alive m8. They wont grow and might stretch a bit but stay alive they will.

They look beautiful by the way and about the FIM.
You know that the new main stems that gets created by a FIM all wont grow out of the FIM cut itself, right? Quite often it makes a branch one step down on the plant start growing as a main stem as well. I have FIM'd 5-6 plants latelly and almost every time that have happened. I get 2-4 stems from the FIM cut and 1-2 of the lower branches start growing as main stems as well. Just take a few days or up to a week and you normally can see if that is happening on the texture of the branch in question.

Good luck with the training and they do look very nice man.

Puffzter