We're building our nesting boxes and ran into a question... Storey's chicken book says to make the nest 14HX14WX12Deep w/ a 4" sill to prevent eggs or nesting materials from spilling out. Dh asked... "so do we build it so that the opening is 10" high b/c of the 4" sill?" Can our Wyandottes, leghorns, etc. get into that opening? or is it 14" above the 4" sill? That would make the box 18" in the front opening. Thanks for any sage advice!