I use a similar setup for my layers but for 100 birds you are going to need at least several of those to have enough trough space for everyone to eat at the same time which is a necessity or some birds hog all the food
I do have one feeder I made with some gutter scraps but I can alreDy tell it isn't going to last as long as the wood ones that have already been in service for 7 or 8 years.
I've not raised that many in one batch myself, but my grandma used to raise 200 or so at a pop. We built her two trough feeders using 1x6 and 1x8 lumber. The 1x8 was the bottom, 2 1x6s for the two sides and then we just used some scraps to create the two ends, plus a brace in the middle. It...