i'm hoping for at least 1 gram per watt at least under 2 x 420w boosted halides. i don't know if i can pull off 400g per square meter though using mostly lower yielding stretchy strains. my understanding of topping is the more bud sites you create, the more top colas your plant thinks it has so instead of 1 big cola, you get a bunch of better than average sized ones with better "light penetration" to boot.
i was actually considering overpacking my screens a little and if they really do start filling up too much, letting them go long enough to prune some end popcorn.
the closest i've gotten to screening was topping my seattle trans-love freebie twice and getting an almost flat top of 8 buds i'd guess were 2 grams each dried when i had to harvest early after everything got burned the night i forgot to turn my fan on after i quit running it 24h to try and get butt sniffing neighbors from hell outta my biz. that was a really compact plant.
the dude that checked out my 1st grow under halide was impressed by how free from spider mites my plants were coming from seed i guess and suggested i let them vedge a lot longer next time as i flipped everything at the 2nd or 3rd node with no topping. my 2 1/2' C99s didn't yield a lot, but i thought if i screened my slower haze skunk, that might have had some serious budding potential as it has a 1 bud per 2 inches flowering pattern that would work better on a screen than vertical i think. i actually did top that one twice too.
i'm not worried about absolute yield, just enough to get me through around half a year with a second harvest to tide me over until next season. in theory, i should get 400g easy with 2 lamps and a couple of 2 1/2' x 3' screens in one harvest. more than anything, i want the best quality THC and flavor expression. i got more complex fruity flavors out of both super cali haze especially and C99 under halide than i did the cross under a sodium which just became "generic fruity" like many other strains.
so far, i think i've yielded way less than that in 2 grows with the second ending in under 45 days of flowering because of the leaf burn. i wish someone would invent a low speed silent fan as regular ones buzz the louder they aren't howling.
idk about topping so much tho, you'd end up with 8 tiny colas compared to what you could have gotten in the first place...
i'm trying to simplify and run fewer plants, that's why i'm looking to max yield per plant instead of pert square meter.