Pure Sativas are hard to grow indoors and you must consider they are a real problem to tune.
Till you're able to tune her well, you will have trouble yelding better; it can also be considered that pure sativas tend not to be great yelders.
With hazes that tipically like to go for 16 weeks+ and streatch from 2" to 4.5', i like to pinch clones at the second node at start and they get much more easy to manage...sometimes, you have to pinch again after 3/4 weeks.
Flower as soon as the clones root or even better, if you can...flower the clones wile they ARE rooting... this is the key to manage extreme sativas indoors.

wolf