its one of those deals where you wont get as much per plant put you will harvest fast/more a year their fore you will yield more, because of the less veg time. allot depends of the strain as always. ive seen some only get 1/4oz per plant and some get 1.5-2oz per plant. allot of the yield is also on the light wattage you use and environment you have.
Irish, I have a strain that only gets aprox 1/4oz per girl of dry bud when doing this 12/12 from the start type of growing method... I do a SOG with 48 girls under a 400w HPS in a 3x3 area.. Growing 12/12 from the start naturally creates lollypops with this strain I have so it saves me from having to manually cut off the lower branches. I do get more grows per year doing it this way.