You should put a little food on the edge so they can see it,once they see the food inside they will take to it fine.It took mine less than 5 minutes to figure it out.
The 3 inch has worked flawlessly for me, the one inch off the bottom I believe is more important as well as having it high enough so they have to stretch a little to get it.
This is the only picture I have at the time, I just filled it today. There is another one on the other side, 3 inch elbows I used the small piece I cut off the elbows and pushed it into the end with the flange to make it stick out a little further don't know if it helps but I had the extra piece...
If they are billing it out it's usually because the hole was drilled to close to the bottom of the bucket, or the elbows were cut to short, basically the farther they have to stick their heads in the less chance of waste. I made this mistake on the first one I made, on the second made the hole...
I went to Lowe's and got 3 inch schedule 40 90 degree elbows with the flange in the plumbing isle.Take away the crumbles and put a few pellets on the edge of the elbows so they can see it, they will eat no chicken ever starved to death when there was food available.
would have at least 2 feeders in with that many chickens just to avoid squabbling, the feed won't go to waste and if they only use one then that's less you'll have to fill it.