New Egg, first of all :
I am no expert but would wood chips (sounds like a limerick, LOL) versus shavings have more splinters? Also are the planer shavings sharp? I wouldn't think so but I am reaching here.
I also find your connection of Leghorns being predisposed to having the issue...
Thank you so much for this post--GREAT job!!
I am getting chicks next spring and have tons of books (yes I've read them too) and want to add these directions and photos to my "Chicken ER" list!