I'll second that... I just did the same thing, the main colas had about 20% amber trichomes so I cut them down about 16" , so the canopy on all of them was about 2' above the planters.
Then lowered the lights to maintain the 20" headroom I prefer and the lower buds doubled in size and got a lot frostier and the trichomes turned to the 15-20% amber that I prefer. Let them go for another 15 days.
I'd never done this before and wasn't sure how to handle the flush period, so I flushed them big time for 5 days before I cut the first colas_2 gallons per plant per day.
Right after I cut the main colas and taped the main stems I watered them with full strength nutrients at a gallon every day for 3 days and then reverted to the every other day watering.
I flushed again for 5 days before harvest and cured the top colas for smoke and made bubble hash from the 2nd harvest using all the buds and sugar trim from the lower portion of the plants. It was the first time I made bubble hash from fresh frozen buds and trim and it is awesome!
I made the bubble hash just a day after harvest. Stuffed gallon sized ziplocks with bud and trim and flash froze them in a cooler with dry ice overnight. Then made the hash using the normal methods. One big difference for me was that the first run with the fresh frozen was by far the best. The 160 and 72 micron screens both produced the best product_ got a blonde sugary, crystal like product from the 160 screen and a shiny, very gooey, very sticky ,very strong, very blonde product from the 72 micron screen.
For some reason the 25 micron screen was just ok and sticky but it was pretty dark green in color...I think that was because chlorophyl in the water was getting trapped by the finer screen. From 6 bags of trim I got about 33 grams of bubble hash, 3 different grades. I tired a second run with the processed weed but it didn't produce near as nice a product so I'll probably just stick with doing one run with the fresh frozen material.
This was one of my most interesting grows and I think I'm going to try the same thing with the next crop.
Best wishes for an awesome harvest!