I am not sure where the idea comes from to thicken the edges of a narrowboat. Some manufacturers do it some don't Personally I like it. It gives a solid look to the boat. So I did my front today.
This is how it started. Thin! (5mm)
Additional part made and spacers inserted
The finished job. Thick (13mm)
Top & both sides done
This all took a lot longer than I would have imagined, but I'm pleased I took my time and got a nice finish ready for painting tomorrow.