Minimal, fortunately. The duct from this fan goes straight up, then curves 90 degrees to meet the duct from the second fan at some sort of "T" that is hidden under duct tape, then takes a straight horizontal shot outside in the same direction without any more bends. I hope there's at least some sort of PVC T hidden under there, but for all I know it's all just plastic duct held together with tape and who knows how restrictive it might be. Not looking forward to cutting a hole in my house, but it might be less trouble than trying to fit a bigger fan in the space. Putting this one in was bad enough.
2D side view in attic (no curves in the Z direction at all):
West wall East wall
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