Thanks for the ideas. Ryan, you are right… it does not scribe well. A test patch showed due to relative softness it is hard top not gouge a line instead of scribe. I am building Yellow 6, which is said to have been on the assembly line with a small group of aircraft that had the larger wood tail as the only modification so the rest of the airframe should be OK as is.
http://hem.passagen.se/galland/kg27.html
The supporting structure is a styrene spine with styrene strips filling and sanded to a basic shape, with coats of Tamiya putty and looks good so far.
Thom, I you are right about CA so I will try “painting” the putty with CA to see if it will harden the surface enough for a better scribe line.