I mean...not meaning to sound like a complete smart @ss, but if your plants don't get growing, your yield will be affected.
Now, if you plan to veg until they are whatever size you are used to, regardless of the time it takes, then the yield should be the same.
In my opinion, your yield depends on the size of the plant when you switch to 12/12 and not so much on what happens before that. So if you get the plant to be filled in and ready to flower before switching the lights, it will produce the yield you would expect from a plant that size. Now, if you have issues in flowering, the yield will be affected.