I am currently building a home with thick foam and using fern strips as a rainscreen/nailer. My father pre-assembled the corner posts on saw horses using 1"X 6" trim boards screwed together to form a typical corner post. Then he nailed the corner to a 3/4" nailer before attaching it to the wall. The nailer which could be any width to suit your foam thickness, was cheated out from the inside corner of the post which left a vent space on the outside corner of the foam. The corner assembly was screwed through the nailer to the framing studs in the corner. Siding was also nailed to this same nailer where it met the corner post. Of course I only am installing a measly 3" of foam to my exterior, but I can assure you it is a pain in the butt, Ah yes the crazy things we will go through to say I have super insulated walls, do you?