OTR Microwave Flex Vent

Someone on these forums, noticed my flex vent going outside from my microwave, and pointed out that flex vents are not recommended and I should have my contractor switch it out for a rigid vent. I checked my microwave's manual and it does say that flex is not recommended, and a rigid vent should be

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Free up space above your cooktop with the new, beautifully designed Smart SLIM Microwave. This combination microwave with ventilation hood fits into the same space as an under-the-cabinet hood, but despite its slim size, it has a sizeable 1.1 cu ft capacity. The SLIM Microwave packs in the powerful performance you need with all the technology that you love in a slim, space efficient size.

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Tight space duct work (7 duct for microwave venting) - is this possible?