filler neck modification

Does one need the restrictor in regions where the pump nozzles have a tight-fitting bellows cover? I don't recall spill-overs in filling my 65 Newport in CA with such nozzles. I haven't been driving my A's regularly to know. As I understand it, without the restrictor, the fill tube doesn't build up enough air back-pressure to trip off the fill nozzle. However, the bellows may work to trap air similarly.