Take some of that foam, cut it into triangular pieces, and shove a piece into every end of the corrugations in the aft baggage area bulkhead.
I did that Bob, No joy. Closed cell foam too.
Also sealed the main spar hole.
I still get that draft up my arm pit. Either foam or a small blanket stuffed in the gaps has been working. Where the heck does that air come from? It is hard to fly and chase drafts.
You need more effort in the spar area. The internal wing area is high pressure, or at least higher than the cabin. I used silicone to seal all air gaps around the spar (there were many surrounding the spar protrusion) and gear leg area (A model). My only drafts are from behind the passenger (slight tip up seal leak and flap rod protrusion). I have none in the crotch area or sides.
Larry