Converting to 12:1 and co2 help.

I have been reading about the 12:1 growing schedule and I'm wanting to convert today lol. I'm in the middle of my veg and want to know if switching them over would start flower? Also I have two mothers in flower three weeks apart and wanted to know if there was any adjustments that could be made there till I can get fresh ones in. Third and last my room is 12x7x8 and wanted to know how I should set my timer to inject (no control in room) and where the ball on my regulator should be.
 
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