@ pagestep007: Many thanks for that tutorial. Will construct the pediment from thin-ish (6mm?) ply; that's still to be determined.

The look I'm going for is this:



The arc may either be painted as a rainbow with a paper mache sun, moon and stars in ascendancy/descendancy, or I may go with a thin tracery of acanthas leaves and medieval marginalia.

oooh , that looks like a delicious project.Maybe 4mm MDF would be good as it goes around curves really well. But yeah, the sun and moon  and   vegetation in  mache would  look really great. A good relief is  always cooler than just painting it on. I like the castle side bits. I take it, that it has to be as light as possible, and remembering  your  location in Greymouth, mache would be a good way to go.
this tutorial may inspire you to  texture your castles.. although it  might add too much weight to  the  stage


this vid  is how I do some ornamental mache-ing. That is if you  have some clay and wax, and like to  sculpt. You could do a plasyter mold...or maybe  just go the  traditional  build it up with paper technique

In the first video you spread down a layer to help bind your plaster to the wood. Since you had your back to the camera it was a bit hard to hear. I thought maybe it was PVA but you kind of troweled it on so not sure.

 

yes it was pva . gloop it on then scape it thin. It just seems to  help make sure  there is  something to stick with and not rely too much on the glue in the mixture.