I have finished the framing and I need to run some lines from the trunk lines into the newly added rooms in my basement. I built soffits around the main/trunk lines and I'm wondering if I should have done the HVAC ducts first. I thought I'd run a rectangular duct through the soffit and just put the vent cover right there on the side of the soffit. Does this sound do-able and what kind of hardware do I need to cut into the trunk line and add the new ducting?