I've only used crumble in it, if it's extra dusty and humid it can plug up.
Another note that is not in the article, might want to use tubing that is larger than 1/2" dia,
one bird can still dig up a pile and drag it out of the feeder.
I haven't experimented with a solution for that.
Says right above the dimensioned drawing.
"Notches where feed comes out are about 1" wide at bottom and 1" tall.
Start notches smaller then enlarge until you find the right size for the feed you are using."
Very nice design and fabrication!
Mine is similar...they still peck and pile and drag feed over the edge.
Here's what I did to keep them from doing that.
Split some 3/8-1/2" tubing..notch the top edge to keep the tubing in place.