So my plan didn’t work, to build up the lip using marine-tex, so my next thought was to use some wood as the primary platform and build up to it.
So I got some pretty sweet free wood from work, and cut off a section to use as the base. I then cut off a small wedge and used that to hold up the ‘lower’ side.
I then used fiberglass to glass the whole thing to the hull
Once i’m sure its cured correctly, I’ll probably put on another couple of layers of glass, then sand it all down and paint the whole area so it looks a lot nicer. I’ll also drill a hole through the middle of the wood and then I can finally mount the chimney!