His notes say it will not work on the welded vent flap. As i have not seen both side by side, are the spot welds in different locations than the bolted vents or are they different sizes? Mine needs a new seal but have never taken it apart to get a good look at it. I have thought about just cutting a piece of 60mil epdm roofing material and using that. The roofing material should stand up to the UV light and assuming that thickness would work, you could make them for less than $10.00 a piece with scraps from a friendly commerical roofer.
@Splangy can you measure the thickness. Again, i have not taken mine apart so if there is more to this, let me know. Also for those who have the bolted flap, any chance you can provide the number of bolts and the size of those bolts? I am thinking it would be best to weld a stud to make mine a bolted flap to make it easier to deal with in the future.