Reply by Cosmicsniper

BTW, 5” ducting is better than 4”. You have to use HVAC ducting for this, but it’s probably worth it. Keep in mind that a 1.5 hp DC is right at the limit of being able to run 6” duct while maintaining enough velocity to still move larger chips. If you try it, you will certainly want to optimize your duct efficiency as much as possible, meaning good connections/transitions, gentle turns, and smooth ducts.

-- jay, www.allaboutastro.com