So ... I'm sitting on the roof of our fifth wheel as I type this
I've removed the old vent, by removing all the old dicor around the vent using a putty knife. I've also cleaned around the area which will be around the new vent flange. (The old dicor and putty was extremely sticky, so it did lift the very thin roof membrane a little, most of the way round, but it mostly seems to be sticking back down onto the plywood roof)
My problem is removing the old putty which was under the flange of the old vent. It's extremely stubborn, even when using isopropyl alcohol.
Do you guys think I really need to remove it all, or would it be okay getting new butyl tape to stick onto a thin layer of the old putty ? (Under the flange).
I'll be using eternabond to cover the flange and seal onto the roof.
Not sure if I can post photos from my phone