would it be possible to put my vegging plants in my tent which is on 12/12 with plants in it,then take them out and put them back under my vegging light for 6 more hours making it 18/6?
it would work but its a pain in the ass... and very prone to human error... there is a very good chance that, even as meticulous as you may be, you will be giving your plants inconsistant light, going against natural cycles...
As long as you don't leave them under 12/12 for more than 2 or 3 days, you won't be at risk of triggering flowering. Be careful Changing the light cycles in conflict with nature can be hazardous to your crop.
not something i would want to do for a long time.
im acually going from outdoor to inside light right now because my new spot isn't done yet. it works, just sucks.