Rough defoliation has to be done ONLY when you have bugs attack that you cant get rid of it by pesticide.
Otherwise, knit your leaves together for helping lower nodes to grow and make tough branches.
you'll have to knit/tie the leaves together everyday but it works.
Defoliation is not bad for the grow period and making many main colas.
But after, in flowering don't remove anything, let the plant sucks what she needs in the leaves when she has to.
Leaves are solar panels as well as energy/sugar containers
another very good point for keeping leaves:
Imagine we have a very hot day, so the plant can get thirsty sooner than expected.
The grower couldn't come soon enough to water her in time.
i.e: he is working at his dayjob and cant go home before the end of his task
Be insured. Extra leaves are there!
the plant can pump a few water from the bottom ones.
You know, those which many growers remove because they are not exposed to the light.
this allows you a few extra time to water.
Then those leaves will dry and fall by themselves FOR THE SAKE of you canopy.