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I like filter questions and I think this one deserves a response although, personally, I can't provide any direct experience with this lens. I can say that I've shot with a 100mm square filter in a filter holder as the third filter out from a 17mm (non-bulbous) lens and that worked ok. I think your idea has a decent chance of working since the built-in hood doesn't appear to extend excessively far beyond the element however even if the coverage is ok, you'll have to find a way to block reflections onto the lens-facing side of the filter. Since you have the lens, you could probably check coverage with a cut 100mm square piece of paper.