It all depends on how hard you treat your boat. A stripper absolutely does flex when it hits things. However, in most cases it does not flex sufficiently to cause a problem because the strips do make it relatively stiff.

While I have gone over obstructions hard enough feel the hull flex enough to make me happy I had foam bulkheads, it is not a common occurrence. But all it takes is one time to make a resilient bulkhead pay.

A foam bulkhead also contributes significantly to the strength of the boat. It may not provide as good deck support as a rigid bulkhead, but it does enough.

I would not try to complicate the bulkhead by trying to make a both rigid and resilient. If you go with a rigid bulkhead glass it in completely. Otherwise go with foam.