I started on the wing root vents. The support tabs are each only attached to the tube with two each aluminum spot welds. I obtained two vents from a Cessna 150 (solid aluminum, as opposed to plastic 172 vents), but one support bracket apparently broke off during pulling from the salvage yard, and another broke off welding that one. Not too sturdy. Accordingly, I TIG welded the detached brackets and augmented the unbroken ones.