Hi!!!!!
So, I stuck some torches on the bamboo at nethergirnder3, it works fine now. Getting a signal down will be a bit harder, bt not impossible.
I wonder if it needs to be so high - bamboo growing the full height of the farm is only a 5% chance, so it might not always fire the breakers.
Better (I think) would be to have a full suite of observers at some lower level, which will mean a higher throughput of bamboo.