Well, I was messing around with connection types and I can emulate the KB duct with "Flange" to "Flange Clamp" connectors. While it doesn't render exactly right (meaning it doesn't look like kb duct physically in the model) it really doesn't matter because it's geometrically correct. I don't know that its really worth the idea board because this is such a specialized duct type. If it ever became more popular though then it'd be worth requesting. Thank you for your response.