First you need to up the CFM requirement with that long of a run . Can you post pics ofyour space that is always helpful A gas or induction range? Waht is above the range placement?

Hello and thanks for getting back to me. The hood we're looking at is 800 CFM and it's a gas range. We currently have builder grade cabinets with a 9' foot ceiling. There should be at least 10 inches above the new cabinets to place 8" inch diameter ducting, and we can put a fascia board in front of the ductwork to hide it. Here are 2 pictures of the existing cabinets. WE intend to extend the cabinets and counter to the exterior wall. Hope this helps.

On long runs they put supplemental fans inside the ductwork. No idea how the requirements are calculated. Maybe an HVAC specialist can help. You will also need them to calculate the make-up air requirements, which can get expensive.

Thanks everyone. if I understand the advice correctly, basically get a bigger hood, and I should use a 45 degree bend and 8 inch ductwork..? is that about right?