From my own results, given the height of the main colas and the amount of free space I'd say around 0.5g per watt of light wouldn't be a bad guess. Maybe a little more if you get lucky. What light are you using? If cobs or qb I'd hope for closer to 1gpw but not with blurps. It's hard to tell even when they're fully grown. Pics can be really deceiving in either direction.
Have a look into topping and lst methods for next grow aswell mate. You've got it sussed so if you were to tie your plants down you could actually improve on your yields by using 2 plants. .see how the main cola is a foot higher than everything else, means everything else is getting a lot less light. Chop the main cola off while theyre still seedlings or tie it down to keep it level with the rest and every cola will turn into a 3/4 main size bad boy. Can take the piss with it and get over 100 colas per plant if you want. It's easy enough like. Just literally tying the branches down during veg so the plant grows horizontally. All there is to it.
If you check the grow review in my sig you'll see what I mean. Not sure what strain you've got there but looks like it's easily capable of the same results.
