here is one almost completed, big improvement I think.
my arches are not exact lol a little like my guesswork,so I put matt board behind the arch and traced the shape onto it.
Then I decided what thickness I wanted the framing to be and cut 2 straight lenghts from matt board the desired width.
I then ran along the edges with an embossing tool to soften them.
The straight section was then used as a measure to draw the thickness of the arch...by simply placing ,marking,placing marking etc then joining the dots.
I then used this as a template for the other side of the archway. The matt board was coloured with a furniture touch up pen ( thanks to MiniAussie) and a small piece of matt board cut to cover the join.I must get back to my shingles now ....oh and the egg cartons are back out for another job this week.