Elastometric foam spacers for bulkhead to hull joint

Are they structural or simply keep the bulkhead separated from the hull and the only structural element is the fiberglass tabbing which joins the bulkhead with hull?

Can a nonstructural spacer be used?

If they are structural, any suggestions for alternative materials?

 

Any soft spacer will work. I have seen rope and bondo used. Foam with beveled edges is my preference.

 

Thanks again