Most strains will double to triple in height during flower and ones that are predominantly sativa and in particular pure sativa will grow more, in some cases MUCH more.
 
When you attempt to decide how tall to veg your plants I always say consider your lighting and your usable growing height/space height and setup in general and then only veg long enough to use all of what your system/setup can actually give you.
There is no sense to vegging a plant to a height so when it takes off in flower it outgrows your lighting. What you get for doing so is making your overall length of time from popping your beans to harvesting longer, paid for more electricity usage, paid for/used more fertilizers/nutrients etc, increased your risk for problems of various sorts and all for what? Some popcorn.
 
Whatever number of days or weeks that would be wasted flowering longer than makes sense for any particular system/setup would much better be used in the popping of your next beans and beginning to veg your next crop.
Even when someone has great lighting and top reflective material if they are new or somewhat new to growing they can still have problems judging what height is best in their situation for beginning flowering, that is unless they use some training method to keep their plants low.
 
Many will look at their grow room and see maybe an 8 foot high ceiling and think they have lots of height to work with. I try to tell new growers to remember that from whatever maximum height the space has you have to subtract the height of the pots you use or the height of your hydro/aero setup and then subtract the height of your light/reflective hood or cfl setup and then subtract the minimum number of inches or feet you need to keep between the top of your plants and the bottom of your lighting and what is left is your maximum amount of usable growing height.
 
So people really need to consider what the maximum height their lighting/reflective material setup can actually provide adequate lighting to and also what actual amount of total height they have to work with and then find a vegging height range that will at least in most cases keep you within the limitations of your setup.
 
Roughly 40% of a yield will come from the outer portions of your plants and those areas can be very difficult to get adequate light to.
If your reflective material is substandard and or if your lighting is not up to the task you give it to perform and it cannot penetrate deep enough, even when combined with your reflective material, and or your lighting just does not cover a large enough footprint then production in those areas will drop off very sharply.