at what point of growth should i cut the large leaves?

[vaping]

when should i cut off the large fan leaves so the bottom stems can get more light?

[Dr FrankenKush]

depends on the strain. I wait till they start to turn yellow at the end usually the bottom is ahead of top anyway a selective pruning in last 3 wks 20 mabe30% won't affect outcome negitively Remember shes gotem for a reason.

[Arising Green]

I wouldn't be choppin any leaves...at any time.

If your light isn't bright enough to penetrate the lower parts of the plant then I
would suggest clipping off those lower branches during late veg/early flower (unless
you don't mind the popcorn/airy buds.) This will also improve the size of the buds left on the plant.

Or try LST.
Just my 2 cents