> Should I be concerned about the bulkhead causing a stress riser?

One might be more concerned about the source of the stress than the potential at the hull/bulkhead joint. That said, if the panels in question were 3mm then spreading the load around would be nice,foam might be better. Or if you were a 250 lb. person carrying 100 lbs. of stuff into the surf alot then the strength/rigidity of the hull and any extra reinforcements would be the first consideration before worrying about the bulkhead/hull question. So I guess the answer is no.