Hi! I was wondering if anyone has tried using step-down rings as replacement lens hoods for their Oly 75mm lens. I currently use a 3rd-party screw-on hood that's about half the length of the lens, so it doesn't do any wonders for portability. I'm hoping that a step-down ring will provide a more compact solution (much like those lens hoods for the Pentax DA 21mm and 40mm lenses). I don't have the luxury of living near a camera store nor have access to an online one with a liberal return policy to try this out myself, so your shared experience will be invaluable. I'm particularly concerned with how small the diameter on the -down end can be before vignetting becomes an issue. TIA!